Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-02-07
2002-01-08
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S124300, C526S124900, C526S124200, C526S158000, C526S125300, C526S128000, C526S130000, C526S348000, C526S348100, C502S125000, C502S126000, C502S127000
Reexamination Certificate
active
06337377
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an olefin-polymerizing catalyst capable of forming in one polymerization system two homopolyolefins, each of said homopolyolefins being an isotactic polyolefin in which the disorder of monomer units alignment is in respective specified range. The present invention further relates to a process for producing an olefin polymer using said catalyst and a polypropylene produced by said process which is useful for production of a biaxially oriented film. More particularly, the present invention relates to a process for producing an olefin polymer excellent in stiffness and stretchability and successfully usable for formation of films, fibers, blow-molded articles, extrusion-molded articles, etc., an olefin-polymerizing catalyst used for production of such a polymer, a polypropylene for use in the production of a biaxially oriented film which can give a biaxially oriented film excellent in transparency and stiffness while retaining a particularly excellent stretchability, and a biaxially oriented film produced from said polypropylene.
DESCRIPTION OF THE RELATED ART
Biaxially oriented films are extensively used as packaging materials because of their excellence in transparency, gloss, stiffness and water vapor barrier property. With the aim of improving the film properties, such as stiffness, of biaxially oriented film, highly crystalline homopolymers of propylene obtained with a high-stereospecificity catalyst have conventionally been used. However, such highly crystalline homopolymers of propylene have a fault that they are inferior in stretchability and apt to make troubles such as film breaking in the course of stretching. Thus, a variety of methods have so far been proposed for improving the stretchability of highly crystalline polypropylene. As one example of such proposals, copolymerization of propylene with a small amount of ethylene is known. Concretely speaking, JP-B-46-11027 has proposed a process for producing a polypropylene for use in production of films which comprises polymerizing propylene together with a very small amount of ethylene in the presence of a coordination catalyst and a hydrocarbon, hydrogen chloride or chlorinated hydrocarbon solvent so that one mole of the monomer unit in the resulting polymer becomes containing 0.01 mole or less of ethylene unit. Further, in JP-B-64-6211, there is proposed a process for producing a polypropylene improved in stretchability which comprises feeding propylene together with a small amount of ethylene into polymerization system using a catalyst consisting of an organoaluminum compound and titanium trichloride prepared by reducing titanium tetrachloride with an organoaluminum compound and further activating the reduced product by a treatment using a complex-forming agent, a treatment using an organoaluminum compound, a treatment using titanium tetrachloride or a combination thereof so that the resulting polymer comes to have an ethylene content of 0.1-1.0% by weight. Further, in JP-B-3-4371, there is proposed a process for producing a biaxially oriented polypropylene film excellent in transparency, stiffness and impact resistance by using a polypropylene of which ethylene content is 0.1-2% by mole and isotacticity is in a specified range. Any of these processes, however, have been unsatisfactory as a method for obtaining a polypropylene for a biaxially oriented film simultaneously having an excellent transparency and a high stiffness while retaining a good stretchability.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an olefin-polymerizing catalyst capable of forming in one polymerization system two homopoly-olefins, each of said homopolyolefins being an isotactic polyolefin in which stereoirregularity of monomer units is in respective specified range, a process for producing an olefin polymer using said catalyst, and a propylene for use in the production of a biaxially oriented film excellent in stretchability and having high transparency and stiffness.
In view of the above-mentioned state of things, the present inventors have conducted extensive studies to find that a polyolefin in which the stereoirregularity is in a specified range can be obtained by using a specified catalyst system, and that a biaxially oriented film simultaneously having high transparency and stiffness while retaining an excellent stretchability can be obtained from a polypropylene obtained by the use of said catalyst system which has a cold decalin-soluble fraction (23° C. decalin-soluble fraction) content falling in a specified range, shows a specified complex elastic molulus in a specified temperature range, and has a melt flow rate (referred to as MFR, too) falling in a specified range. Based on this finding, the present invention has been accomplished.
Thus, the present invention relates to a process for producing an olefin polymer which comprises homo- or co-polymerizing an olefin by the use of a olefin-polymerizing catalyst consisting of:
(A) a solid catalyst component containing magnesium, titanium, halogen and an electron donative compound as essential components,
(B) an organoaluminum compound, and
(C) at least two electron donative compounds including electron donative compound (&agr;) and electron donative compound (&bgr;), provided that 105° C. xylene-insoluble fraction of a homopolypropylene obtained by carrying out a polymerization using the electron donative compound (&agr;) together with the solid catalyst component and the organoaluminum compound shows a pentad stereoirregularity index (mmrr/mmmm) satisfying the following formula:
0≦mmrr/mmmm≦0.0068
and 105° C. xylene-insoluble fraction of a homopolypropylene obtained by carrying out a polymerization using the electron donative compound (&bgr;) together with the solid catalyst component and the organoaluminum compound shows a pentad stereoirregularity index satisfying the following formula:
0.0068≦mmrr/mmmm≦0.0320;
an olefin-polymerizing catalyst consisting of:
(A) a solid catalyst component containing magnesium, titanium, halogen and an electron donative compound as essential components,
(B) an organoaluminum compound, and
(C) at least two electron donative compounds including electron donative compound (&agr;) and electron donative compound (&bgr;), provided that 105° C. xylene-insoluble fraction of a homopolypropylene obtained by carrying out a polymerization using the electron donative compound (&agr;) together with the solid catalyst component and the organoaluminum compound shows a pentad stereoirregularity index (mmrr/mmmm) satisfying the following formula:
0≦mmrr/mmmm≦0.0068
and 105° C. xylene-insoluble fraction of a homopoly-propylene obtained by carrying out a polymerization using the electron donative compound (&bgr;) together with the solid catalyst component and the organoaluminum compound shows a pentad stereoirregularity index satisfying the following formula:
0.0068≦mmrr/mmmm≦0.0320;
and a polypropylene for use in the production of a biaxially oriented film obtained by carrying out a polymerization using said catalyst system, wherein:
(1) the content of 23° C. decalin-soluble fraction of the polypropylene is in the range of from 3.0 to 10.0% by weight,
(2) when a vibration of 110 Hz is applied to the polypropylene, the polypropylene shows a complex elastic modulus of 1.0×10
9
dynes/cm
2
at a temperature falling in the range of from 134° C. to 152° C., and
(3) melt flow rate (MFR) of the polypropylene at 230° C. is in the range of from 0.5 to 10.0 g/10 minutes.
Further, the present invention relates also to a biaxially oriented film obtained by subjecting said polypropylene for use in the production of biaxially oriented film to a stretching processing.
Next, the present invention is explained below in more detail.
The catalyst system used for production of the polyolefin of the present invention consists of (A) a solid catalyst component containing magnesium, titanium, halogen and electron donative component as essential compo
Ebara Takeshi
Kimura Jun-ichi
Mizunuma Koji
Obata Yoichi
Sasaki Toshio
Choi Ling-Siu
Fitch Even Tabin & Flannery
Sumitomo Chemical Company Ltd.
Wu David W.
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