Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-02-14
2003-05-27
Lu, Caixia (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S124300, C526S124500, C526S165000, C526S348000, C526S124900, C502S120000, C502S125000, C502S132000
Reexamination Certificate
active
06569964
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to transition metal-based olefin polymerization Ziegler-Natta catalysts, methods of making the same and methods of using the same.
2. Description of Related Art
Several publications are referenced in this application. These references describe the state of the art to which this invention pertains, and are incorporated herein by reference.
In the field of olefin catalysis, there have been many remarkable discoveries during the last 50 years. In particular, two broad areas of invention stand out. Firstly, in the 1950's, the Ziegler or Ziegler-Natta type catalysts were discovered and exploited for a variety of applications. Today, these catalyst systems, most often referred to as Ziegler-Natta catalysts, are used extensively in commercially important industrial operations. Secondly, and more recently, the discovery of “Metallocene” catalysts having cyclopentadieneyl-modified transition metal complexes has advanced polyolefins research and commercialization.
However, despite the progress in these areas, there are still certain limitations as recognized by those of ordinary skill in the art. For example, traditional Ziegler-Natta catalysts (hereafter referred to as Z-N catalysts) often display limited productivity, where productivity is defined as the efficiency of conversion of monomer to useful polymer per unit of transition metal catalyst utilized.
In contrast, metallocene-based catalysts intrinsically possess high rates of productivity. Typically, however, commercial plants are not able to use such high levels of productivity and refitting such plants would be prohibitively expensive. That is, many commercial plants are not able to use such high levels of productivity because the amount of polymer is in excess of the downstream equipment's ability to process the product. Additionally, the resultant polymers often have undesirable physical characteristics such as very low bulk density and a very narrow molecular weight distribution. These factors, among others, may be seen to negatively impact the commercial utility of these metallocene-based catalyst materials.
To overcome these limitations, the so-called metallocene catalyst systems have often been modified by incorporating the catalysts with non-metallocene catalyst systems thus yielding commercial polymers having an acceptable balance of properties. However, preparing such multi-component catalysts is cumbersome and expensive.
U.S. Pat. Nos. 4,701,423 and 5,183,867 to Welborn, Jr., et al., describe supported olefin polymerization catalysts and processes of using the same. These catalysts may contain at least one metallocene compound of a metal of Group IVB, VB, and VIB of the Periodic Table, a non-metallocene transition metal containing compound of Group IVB, VB, or VIB metal and an alumoxane. The catalysts are reaction products formed in the presence of a support. Welborn describes the utility of the catalysts for the polymerization of olefins, especially ethylene and especially for the copolymerization of ethylene and other mono- and diolefins. More specifically, the Welborn '423 patent describes supported olefin catalyst systems wherein the catalyst components consist of a metallocene, a nonmetallocene transition metal component, an alumoxane and optionally, a cocatalyst system of an organic compound of a metal of Groups I-III of the Periodic Table, particularly, those known in the art as aluminum alkyls. The Welborn '867 Patent also relates to the use of a two component transition metal complex wherein alumoxane and, optionally, aluminum alkyls are used to prepare polymers having multimodal molecular weight distributions (MWD).
U.S. Pat. No. 4,303,771 to Wagner, et al., relates to a catalytic process for preparing ethylene polymers having a density ranging from greater than or equal to 0.94 to less than 0.97 g/cm
3
and a melt flow rate of about 22 to about 32 in a low pressure reactor at a productivity of greater than or equal to 50,000 lbs of polymer per pound of titanium with a catalyst formed from selected organoaluminum compounds and a precursor composition being the reaction product of titanium trichloride, magnesium dichloride and an electron donor (ED) compound such as tetrahydrofuran in specific ratios. This precursor is used as a “partially activating” compound before being introduced into a polymerization reactor.
U.S. Pat. No. 4,302,566 to Karol, et al., also relates to the preparation of transition metal catalysts supported on an inert carrier material and reacted with selected organoaluminum compounds. Additionally, the Karol '566 patent relates to specific activation sequences for the catalytic entities.
U.S. Pat. No. 4,124,532 to Giannini, et al., describes the usefulness of incorporating various alkali and alkali earth metal complexes, e.g., magnesium dichloride, into olefinic transition metal polymerization catalysts. These compounds are disclosed as having a positive effect on the activity of the polymerization of ethylene and alpha-olefins while generally being much less active than the corresponding transition metal halides.
In view of the prior art limitations, it would be useful to provide methods of producing homo- and copolyolefin polymers with catalysts which overcome the above-described stated limitations of the conventional catalyst systems. In particular, it would be useful to provide for increased productivity while concomitantly broadening the molecular weight distribution while maintaining relatively consistent values of bulk density. These advantages would be recognizable to those of ordinary skill in the catalyst and polymerization arts as commercially valuable. An improvement in productivity means that less catalyst is more economically consumed resulting in a cost savings in the amount of catalyst used to produce a given quantity of polymer.
Additionally, as with most industrial polymers, there are differences between the desired material properties and those which result from a typical production operation. Accordingly, it would also be desirable to positively affect the productivity of the catalyst while minimizing changes in the bulk density of the materials produced. This is particularly true since bulk density significantly affects the commercial aspects of polymers, e.g., the shipping of and handling of the polymer materials.
Therefore, it would be advantageous to have a catalyst system having a productivity typically higher than traditional Z-N systems, but without the inherent tradeoffs including the narrowing of the molecular weight distribution and the decrease in the bulk density which occur with metallocene catalysts systems. Thus, a second useful advantage in an olefinic catalyst system would be improving the physical properties of the polymers produced (especially a wide molecular weight distribution) while maintaining a constant value for the bulk density. A polyolefin having these characteristics would be more suitable for different kinds of processing operations (e.g., molding) and particularly, injection molding and film fabrications operations. Still another advantage in an olefinic catalyst system would be the significantly increased flexibility in preparing various combinations of cocatalyst systems useful for polymerization of olefins monomers.
OBJECTS OF THE INVENTION
It is an object of the invention to overcome the above-identified deficiencies.
It is another object of the invention to provide a catalyst for use in olefin polymerizations having a useful, improved range of productivity and methods of using the same.
It is a further object of the invention to provide a method of making improved catalysts for use in olefin polymerizations.
It is a still further object of the invention to provide methods of making improved polymer products from olefin polymerizations having improved physical properties including improved molecular weight distributions, single melting point peak, and/or improved bulk density.
The foregoing and other objects and advantages of the inve
Abu-Raqabah Atieh
Al-Sádoun Abdul Wahab
Nallaveerapan Navin
Kramer Levin Naftalis & Frankel
Lu Caixia
Saudi Basic Industries Corporation
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