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
2002-02-25
2003-10-28
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...
C525S240000
Reexamination Certificate
active
06639018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polypropylene resin composition and a process for producing the same. More particularly, the present invention relates to a polypropylene resin composition excellent in rigidity, impact resistance and balance of these properties, and to a process for producing the same.
2. Description of Prior Arts
Polypropylene resins such as propylene homopolymers, propylene-based block polymers and propylene-based random copolymers are used in wide applications due to relatively excellent rigidity and impact resistance. As the polypropylene resin, propylene homopolymers, propylene-based block polymers and propylene-based random copolymers are generally known.
The propylene-based block polymer is a propylene resin composition obtained by copolymerizing propylene with ethylene and/or &agr;-olefin having 4 or more carbon atoms to produce a copolymer part in which a repeating unit derived from propylene, a repeating unit derived from ethylene and/or a repeating unit derived from the &agr;-olefin are randomly bonded and subsequently copolymerizing those to produce a copolymer part having a different structure from that of the above-mentioned copolymer part, in which a propylene repeating unit, an ethylene repeating unit and/or the &agr;-olefin repeating unit are randomly bonded.
However, a film obtained by using the propylene-based block copolymer is inferior in film appearance such as transparency as compared with a film obtained by using a propylene homopolymer or propylene-based random copolymer, therefore, particularly in the field of films, propylene homopolymers or propylene-based random copolymers are used.
For example, JP57-185336A describes a polypropylene resin composition composed of (I) a crystalline propylene homopolymer or copolymer of propylene with another &agr;-olefin having an intrinsicviscosity [&eegr;] of 0.6 to 2.5 dl/g, and (II) a crystalline propylene homopolymer or copolymer of propylene with another &agr;-olefin having an intrinsic viscosity [&eegr;] of 2.5 to 10 dl/g and an intrinsic viscosity [&eegr;] 2-fold or more of that of (I), which has a molding processability improved without damaging mechanical properties such as rigidity, impact resistance and the like, transparency, heat resistance and chemical resistance and which avoids a trouble of fish eye generation.
However, the polypropylene resin composition disclosed in the above-mentioned JP 57-185336A is insufficient in impact resistance though it is high rigidity due to high crystallinity, since the lower molecular weight component (I) used in examples of the above-mentioned JP 57-185336A has an isotactic index of at least 94.8% and the higher molecular weight component (II) has an isotactic index of at least 92.3%. Therefore, improvement in balance of rigidity and impact resistance is desired.
Further, JP06-240068A discloses a polypropylene composition containing an ultrahigh molecular weight polypropylene having an intrinsic viscosity of 5.0 dl/g or more and a low molecular weight polypropylene having an intrinsic viscosity of 0.03 to 3.5 dl/g and an isotactic pentad fraction of 0.960 or more, which is excellent in mechanical properties such as rigidity, heat resistance and the like and has excellent flowability in molding.
However, the ultrahigh molecular weight polypropylene having an intrinsic viscosity of 5.0 dl/g or more used in examples of the above-mentioned JP06-240068A is polymerized according to a method described in JP03-007704A, and an ultrahigh molecular weight polypropylene described in JP03-007704A has an isotactic pentad fraction of 0.960 or more. Further, the above-mentioned low molecular weight polypropylene used in the JP06-240068A also has an isotactic pentad fraction of 0.960 or more. Therefore, also the above-mentioned polypropylene composition described in the JP06-240068A has insufficient impact resistance, consequently, there is a desired for improvement in balance of rigidity and impact resistance.
JP06-248133A describes a polypropylene composition composed of (IA) a high molecular weight polypropylene having an intrinsic viscosity [&eegr;] of 1.0 or more and a pentad fraction of 0.90 or more and (IIA) a highly stereoregular polypropylene having a [&eegr;] of 0.1 to 0.8 and a pentad proportion of 0.93 or more, which is rich in molding processability and has good balance in physical properties between rigidity and impact resistance.
However, the rigidity of the composition does not necessarily sufficient. Therefore, for sufficiently improving the rigidity by using the IIA, it is necessary to increase the use amount of the IIA, and resultantly, impact resistance becomes insufficient, and also the above-mentioned polypropylene composition described in JP06-248133A is desired to have improved rigidity and balance of rigidity and impact resistance.
SUMMARY OF THE INVENTION
In view of the above-mentioned situations, the present inventors have intensively studied, and resultantly, found that a polypropylene resin composition having a specified melt flow, comprising: a propylene-based polymer (A) having a specified intrinsic viscosity and melting point; and a propylene-based polymer (B) having a specific intrinsic viscosity and melting point, can solve the above-described problems, leading to completion of the present invention.
An object of the present invention is to provide a polypropylene resin composition excellent in rigidity, impact resistance and balance of rigidity and impact resistance and a process for producing the polypropylene resin composition.
Namely, the present invention relates to a polypropylene resin composition having a melt flow rate of 0.5 to 20 g/10 min., comprising 20 to 98 parts by weight of a propylene-based polymer (A) having an intrinsic viscosity [&eegr;] measured in tetralin at 135° C. of 2.0 to 5 dl/g and a melting point (Tm) determined from the peak temperature of the melting curve measured by a differential scanning calorimeter (herein-after, abbreviated as “DSC”) of 140 to 162° C. and 2 to 80 parts by weight of a propylene-based polymer (B) having an intrinsic viscosity [7 ] measured in tetralin at 135° C. of 0.80 to 1.8 dl/g and a melting point (Tm) determined from the peak temperature of the melting curve measured by DSC of 160 to 166° C., and a process for producing the resin composition.
The present invention will be described in detail below.
DETAILED DESCRIPTION OF THE INVENTION
The propylene-based polymer A and the propylene-based polymer B used in the present invention are propylene homopolymers or propylene-based random copolymers.
The propylene-based random copolymer is a random copolymer obtained by copolymerizing propylene with ethylene and/or at least one comonomer selected from &agr;-olefins having 4 to 20 carbon atoms.
Examples of the &agr;-olefin having 4 to 20 carbon atoms include 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl -1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl -1-pentene, 3,3-dimethyl-1-butene, 1-heptene, 5-methyl-1-hexene, 3,4-dimethyl-1-pentene, 4-ethyl-1-pentene, 4-trimethyl-1-butene, 3-methylethyl-1-butene, 1-octene, 4-methyl-1-pentene, 5-ethyl-1-hexene, 4,5-dimethyl-1-hexene, 6-propyl-1-heptene, 5,6-methylethyl-1-heptene, 5-trimethyl-1-pentene, 4-propyl-1-pentene, 3-diethyl-1-butene, 1-nonene, 1-decene, 1-undecene, 1-dodecene and the like. Preferable are 1-butene, 1-pentene, 1-hexene and 1-octene, more preferable are 1-butene and 1-hexene.
Examples of the propylene-based random copolymer include a propylene-ethylene random copolymer, propylene-&agr;-olefin random copolymer, propylene-ethylene-&agr;-olefin random copolymer and the like.
Examples of the propylene-&agr;-olef in random copolymer include a propylene-1-butene random copolymer, propylene-1-hexene random copolymer and the like, and examples of the propylene-ethylene-&agr;-olefin random copolymer include a propylene-ethylene-
Ebara Takeshi
Obata Yoichi
Yunoki Shunji
Birch & Stewart Kolasch & Birch, LLP
Nutter Nathan M.
Sumitomo Chemical Company Limited
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