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
2000-11-27
2001-11-06
Seidleck, James J. (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...
C526S351000, C526S352000, C526S124200, C526S124300, C526S124500, C526S125100, C526S116000
Reexamination Certificate
active
06313227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a propylene-ethylene block copolymer, a method for producing it, a resin composition containing the copolymer, and a blow-molded article of the copolymer. More precisely, the invention relates to a propylene-ethylene block copolymer having good heat resistance and good drawdown resistance and having well-balanced rigidity and impact resistance, especially well-balanced rigidity and low-temperature barrier resistance; to an efficient method for producing the copolymer; to a resin composition containing the copolymer; and to a blow-molded article of the copolymer or the resin composition, which is especially favorable to large-size parts of automobiles such as bumpers, etc.
2. Description of the Related Art
As a rule, polypropylene resins have characteristics of low specific gravity, high rigidity, good dimensional stability and good heat resistance. As being general-purpose resins, therefore, they are molded into articles of desired shapes in various molding methods of, for example, extrusion molding, injection molding, blow molding, etc. Above all, blowmolding is much employed for molding large-size structural members such as typically automobile parts, since molds for it are inexpensive and since its process can be simplified by integrating the process steps. However, blow-molded articles of ordinary polypropylene resins are not always satisfactory in point of the moldability, especially the drawdown resistance, and of the balance of rigidity and impact resistance, especially the balance of rigidity and low-temperature barrier resistance. Therefore, various attempts have been made for solving the problem with polypropylene resins by employing multi-stage polymerization for producing the resins and by adding a nucleating agent to the resins (e.g., Japanese Patent Publication No. 74264/1991, Japanese Patent Laid-Open No. 213547/1988). In particular, for large-size blow-molded articles, polypropylene resins are combined with polyethylene resins for improving their drawdown resistance, and inorganic fillers such as talc and the like are added thereto for compensating for the reduction in the rigidity of the resin blends. However, these result in increasing the weight of the resin moldings.
We, the present inventors have previously found out a technique of improving the rigidity and the drawdown resistance of large-size blow-molded articles of polypropylene resins (WO96/02381). With the recent requirements of weight reduction (for example, wall thickness reduction) and weather resistance with automobile materials, desired is further improving the rigidity and the impact resistance, especially the low-temperature barrier resistance of polypropylene resins.
SUMMARY OF THE INVENTION
In that situation, the present invention is to provide a propylene-ethylene block copolymer having good heat resistance and drawdown resistance and having well-balanced rigidity and impact resistance, especially having good low-temperature barrier resistance, a composition containing it, and a blow-molded article of the copolymer or the resin composition especially favorable to large-size parts of automobiles such as bumpers, etc.
We, the present inventors have assiduously studied so as to attain the object as above, and, as a result, have found that a high-stereospecificity propylene-ethylene block copolymer having specific polymer characteristics and a resin composition comprising the copolymer and containing an antioxidant and a nucleating agent can attain the object. We have further found that the propylene-ethylene block copolymer can be efficiently produced through multi-stage polymerization in the presence of a specific catalyst system. On the basis of these findings, we have completed the invention.
Specifically, the invention provides the following:
(1) A propylene-ethylene block copolymer having a melt flow rate (MFR), measured at a temperature of 230° C. and under a load of 2.16 kgf (21.2 N), of from 0.01 to 1.0 g/10 min, and comprised of (A) from 85 to 97% by weight a 25° C. xylene-insoluble fraction and (B) from 3 to 15% by weight of a 25° C. xylene-soluble fraction, wherein the fraction (A) is characterized in that (a-1) its stereospecificity index [mmmm] measured through isotopic carbon nuclear magnetic resonance (
13
C-NMR) is at least 98.0%, (a-2) its intrinsic viscosity [&eegr;] measured in tetralin at 130° C. falls between 2.5 and 5.5 dl/g, and (a-3) its weight-average molecular weight, Mw, measured through gel permeation chromatography (GPC), and the content, S (% by weight), of the fraction having a molecular weight of at most 10
4.5
therein satisfy the following formula (I):
S≦−
5.3×10
−6
Mw+
7.58 (I)
where Mw indicates the weight-average molecular weight of the fraction (A),
and the fraction (B) is characterized in that (b-1) its ethylene unit content measured through
13
C-NMR falls between 30 and 70% by weight, and (b-2) its intrinsic viscosity [&eegr;] measured in tetralin at 135° C. falls between 2.5 and 9.0 dl/g;
(2) A method for producing the propylene-ethylene block copolymer of above (1), for which propylene and ethylene are polymerized through multi-stage polymerization in the presence of a high-stereospecificity catalyst system that comprises (C) a solid catalyst component formed from (c-1) a magnesium compound, (c-2) a titanium compound, (c-3) an electron donor, and optionally (c-4) a silicon compound, (D) an organoaluminium compound, and (E) an electron-donating compound;
(3) A resin composition comprising the propylene-ethylene block copolymer of above (1), an antioxidant, and a nucleating agent;
(4) A blow-molded article of the propylene-ethylene block copolymer of above (1); and
(5) A blow-molded article of the resin composition of above (3).
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Nakagawa Masaru
Nakamura Tetsuya
Sugita Yasuhisa
Tanaka Kenji
Asinovsky Olga
Idemitsu Petrochemical Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Seidleck James J.
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