Chemistry of hydrocarbon compounds – Product blend – e.g. – composition – etc. – or blending process... – Component of indefinite molecular weight greater than 150
Reexamination Certificate
2000-06-02
2002-06-18
Howard, Jacqueline V. (Department: 1764)
Chemistry of hydrocarbon compounds
Product blend, e.g., composition, etc., or blending process...
Component of indefinite molecular weight greater than 150
C585S018000, C585S511000, C585S525000, C502S169000, C502S202000, C502S226000
Reexamination Certificate
active
06407299
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the oligomerization and polymerization of ethylene and &agr;-olefins using a two part catalyst system comprising an alkyl magnesium component and a Lewis acid. The products range from highly linear, high molecular weight, solid polymers to highly branched, lower molecular weight oils.
BACKGROUND OF THE INVENTION
The polymerization of ethylene, propylene and other &agr;-olefins catalyzed by transition metal catalyst systems has been practiced commercially for many years. For example homo- and copolymers of ethylene with other materials such as olefins (acyclic and/or cyclic, optionally substituted), and other types of monomers, are being used as plastics for packaging materials, molded items, films, etc., and as elastomers for molded goods, belts of various types, in tires, adhesives, and for other uses. It is well known in the art that the structure of these various polymers, and hence their properties and uses, are highly dependent on the catalyst and specific conditions used during their synthesis. In addition to these factors, processes in which these types of polymers can be made at reduced cost are also important. Therefore, improved processes and catalyst systems for making such polymers are of great commercial interest.
Catalysts used in polyolefin preparation can be classified into a limited number of types. Ziegler-Natta type catalysts for polymerization of unsaturated hydrocarbons, such as &agr;-olefins, have long been the state of the art catalysts for such reactions. Typically, Ziegler-Natta type catalysts are composed of transition metal salts and aluminum alkyl compounds. While these catalysts are very effective and have a long-established record of use, they are not without drawbacks. For example, transition metals are expensive, potentially present some toxicity hazards, and to some extent are environmentally objectionable. Therefore, continuing efforts towards development of other suitable olefin polymerization catalysts have occurred. For example, metallocene catalysts have been developed for use in &agr;-olefin polymerizations. Even more recently, there have been attempts to use non-transition metal catalysts like Al compounds. For example, there are cationic Al compounds disclosed in U.S. Pat. No. 5,777,120 and neutral Al compounds disclosed by Sen et al. (Polym. Prepr. 34 (2) 818 (1998)). However, until the present invention, combinations of non-transition metal catalysts (e.g. Mg and Al) for these purposes were unknown.
The polymerization of ethylene and &agr;-olefins typically leads to the formation of highly linear polymers. One use for these polymers, when in a fluid form, is for synthetic lubricant compositions. However, polymerization of ethylene, the most widely available and least expensive of the olefins, by transition metal catalysts usually leads to the formation of solid polymers. Thus polyethylene is commonly used to make plastic containers such as milk jugs and for plastic films. As such, polyethylene is generally not suitable for use as soft materials or lubricants for most applications. Thus significant research continues to be performed to discover improved methods for synthesizing liquid polyolefins, especially polyethylene.
In general, synthetic lubricants are more desirable as they tend to provide lower friction and increased mechanical efficiency across the full spectrum of mechanical loads and do so over a wider range of operating conditions relative to traditional oil lubricants. The objective of industrial research on synthetic lubricants is, in general, to achieve a polymeric fluid that exhibits a useful viscosity over a wide range of temperature, i.e., has a good viscosity index (VI), while also exhibiting good lubricity, and a pour point equal to or better than mineral oil. One characteristic of the molecular structure of the polymeric fluids has been found to correlate very well with all of these desirable lubricant properties. This characteristic is the polymer's branching index, BI. BI is the ratio of methyl protons to total non-aromatic, aliphatic group protons in the polymer product. The BI of a polymer is easily determined from proton NMR spectra by calculating the ratio of non-aromatic methyl hydrogens centered around 0.85 ppm, to the total non-aromatic aliphatic hydrogens in the range of 0.5 to 2.1 ppm. BI is related to the number of branches (n) per 1000 methylene (CH
2
) groups in the following way: BI=3n/2000.
Generally, as the BI increases, the pour point of the polymer fluid, i.e., the temperature at which the composition changes from a liquid to a solid, decreases. This is a desirable effect as a lower pour point extends the application range of the polymer fluid. BI, however, has a negative effect on the viscosity index of a polyethylene oil; it is well-known in the art that the viscosity index of polyethylene fluids decreases as the branching index increases. This is an undesirable effect because a lower viscosity index indicates a poor viscosity-temperature performance. Thus, the challenge in synthesizing polyethylene fluids is to achieve an amount of branching sufficient to maintain the polyethylene in a liquid state such that the polyethylene fluid has a good viscosity index.
Recently there have been a number of discoveries in the synthesis of branched polyethylene polymers. For example, DuPont and the University of North Carolina, have developed novel Ni(II) and Pd(II) based catalysts which catalyze the polymerization of ethylene to form polyethylene liquids. In this PCT Application (No. WO 96/23010) it has been disclosed that polymers having a moderate degree of branching can be synthesized by using palladium and nickel catalysts incorporating very bulky chelating &agr;-diimine bidentate ligands. The PCT application discloses, for example, polyolefins having about 80 to about 150 branches per 1000 methylene groups, wherein for every 100 branches that are methyl branches, there are about 30 to about 90 ethyl branches, about 4 to about 20 propyl branches, about 15 to about 50 butyl branches, about 3 to about 15 amyl branches, and about 30 to about 140 hexyl or longer branches. The olefin polymers described in the PCT application are said to be usefull as elastomers, molding resins, in adhesives, etc. Polymers containing monomer units derived other than from olefins are also disclosed in the PCT application; and polymers which contain olefin and olefinic ester monomer units, particularly copolymers of ethylene and methyl methacrylate and/or other acrylic esters, are said to be useful as viscosity modifiers for lubricating oils. The basis for the above PCT Application is believed to be an article by Johnson et al published in the Journal of the American Chemical Society (
New Pd
(
II
)
and Ni
(
II
)-
Based Catalysts for Polymerization of Ethylene and
&agr;-
Olefins
, J. Am. Chem. Soc. 1995, 117, 6414-6415). In these systems, however, the degree of branching is only 20 to 150 branches per 1,000 CH
2
groups.
Other highly active Nickel(II) and Palladium(II)-based catalysts have been discovered by researchers at The Pennsylvania State University and have been employed for the preparation of highly branched polyethylene fluids having greater than 587 branches per 1000 CH
2
groups. These polymers and their synthesis have been reported by J. S. Kim, J. H. Powlow, L. M. Wojcinski, S. Murtuza, S. Kacker, and A. Sen, “
Novel Nickel
(
II
)
and Palladium
(
II
)-
Based Catalyst Systems for the Synthesis of Hyperbranched Polymers from Ethene
”, J. Am. Chem. Soc. 120, 1932, 1998. Such highly branched polymers, however, have a VI that typically is too low to be used as, for example, a lube basestock. See also WO 98/33823 titled “Metal Catalyzed Synthesis of Hyperbranched Ethylene and/or &agr;-olefin Polymers”.
Another recent international patent application (PCT Application No. WO 97/02298) relates to the preparation of polyolefins by coordination polymerization of ethylene, styrene or norbornene using a catalyst comprising (a) a zerovalent tricoordinate or
Kim Jang Sub
Sen Ayusman
ExxonMobile Research and Engineering Company
Howard Jacqueline V.
Peist Kenneth W.
Wang Joseph C.
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