Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
1999-09-10
2001-12-25
Wu, David W. (Department: 1713)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C556S054000, C556S013000, C556S019000, C502S150000, C526S172000
Reexamination Certificate
active
06333423
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to catalytic polymerization of alpha-olefins, and more particularly, to an ultra-high activity non-metallocene pre-catalyst featuring an amine bis(phenolate) ligand-metal chelate and a method for catalytic polymerization of alpha-olefin monomers using this pre-catalyst.
Currently, there is significant interest relating to methods and systems of catalytic polymerization of alpha-olefin monomers based on a ‘pre-catalyst’ featuring a metal bound to one or more spectator ligands, where the pre-catalyst may be soluble in a liquid phase solvent, or is adsorbed on a solid surface, and where alpha-olefin monomer reactant may be liquid or gas phase. In such methods and systems, typically, the pre-catalyst is activated by at least one ‘co-catalyst’, where the combination of the activated pre-catalyst and the at least one co-catalyst functions as a single chemical entity, or complex ‘catalyst’, for polymerization of the alpha-olefin monomer. The field of catalytic polymerization of alpha-olefin monomers is of significant industrial importance, as more than 50 million tons of poly(alpha-olefin) products, such as polyetheylenes and polypropylenes, are produced each year, involving metal based catalytic processes and systems.
Hereinafter, the term ‘pre-catalyst’ refers to a chemical entity, in general, and to a chemical compound, in particular, which, when activated by at least one ‘co-catalyst’, becomes part of a ‘catalyst’ functional for catalytic polymerization of an alpha-olefin monomer, under proper polymerization reaction conditions. Without the presence of at least one co-catalyst, a pre-catalyst is ineffective for catalytic polymerization of an alpha-olefin monomer, and consequently exhibits essentially no catalytic activity for polymerization of an alpha-olefin monomer. Here, when referring to catalytic activity during a polymerization reaction, reference is with respect to the catalytic activity of a pre-catalyst, and it is to be understood that the pre-catalyst is functioning in concert with at least one co-catalyst for effecting catalytic polymerization of an alpha-olefin monomer. Thus, the present invention focuses on a new and novel pre-catalyst compared to pre-catalysts currently used for catalytic polymerization of alpha-olefin monomers.
Currently, one of the major goals in this field is to produce a variety of new types of poly(alpha-olefin) products, for example, polymers made from alpha-olefin monomers featuring more than three carbon atoms such as 1-hexene, having well defined physicochemical properties and characteristics, such as mechanical strength, elasticity, melting point, and chemical resistance, applicable for manufacturing a diversity of end products. This may be achieved by polymerizing different types of alpha-olefin monomers, in order to produce a variety of homo-polymers and co-polymers, with varying degrees of monomer incorporation.
Typically, degree of monomer incorporation strongly depends upon catalyst activity for polymerization of a given alpha-olefin monomer. Recently, Britovsek, G. J. P., et al., in “The Search For New-Generation Olefin Polymerization Catalysts: Life Beyond Metallocenes”,
Angew. Chem. Int. Ed. Engl.
38, 428-447, 1999, provided a practical quantitative ranking of catalytic activity, with respect to weight of a pre-catalyst, (grams polymer produced)/(mmole-pre-cat. hr), for ethylene polymerization, under one bar pressure, as follows: very low<1, low 1-10, moderate 10-100, high 100-1000, very high>1000. Their ranking is derived from data of catalytic polymerization of ethylene, which is the easiest alpha-olefin monomer to polymerize. Catalytic activity for polymerization of other larger alpha-olefin monomers, such as 1-hexene and 1-octene, is usually at least one order of magnitude less. Thus, a pre-catalyst for polymerization of 1-hexene, for example, may be considered exhibiting high, and very high, activity in the range of about 10-100, and 100-1000, grams/(mmole-pre-cat. hr), respectively.
Physicochemical properties of polymers include, are directly related to, and are controllable by, polymer molecular weight and molecular weight distribution. These values are highly relevant with respect to producing different types of polymers. For example, ultra-high molecular weight polyethylene (UHMWPE), having an average molecular weight above 3,000,000 has the highest abrasion resistance of thermoplastics and a low coefficient of friction. Unlike synthesis of small molecules, however, polymerization reactions involve random events characterized by formation of polymers having a range of molecular weights, rather than a single molecular weight. Typically, polymers are better defined and characterized in relation to narrow molecular weight ranges.
The accepted parameter for defining polymer molecular weight distribution is the polydispersity index (PDI), which is the weight average molecular weight, M
w
, divided by the number average molecular weight, M
n
, or, M
w
/M
n
. Depending upon the actual application, ideally, a catalytic polymerization system features ‘living’ polymerization in which the rate of initiation is higher than the rate of propagation leading to a PDI of close to 1, and involving a single catalytic active site. This has been achieved in very few systems for catalytic polymerization of alpha-olefin monomers. A PDI of 2.0, signifying ‘non-living’ polymerization, is often found in metallocene catalytic systems, also involving a single catalytic active site. Classical heterogeneous Ziegler-Natta catalytic systems usually lead to a broader range of molecular weights with a PDI of about 5. One current challenge is to design alpha-olefin polymerization pre-catalysts, and catalytic systems including such pre-catalysts, leading to poly(alpha-olefin) products with low values of PDI.
Metallocene pre-catalysts, featuring a metal complex including a metal atom, for example from Group IV transition elements such as titanium, zirconium, and hafnium, bound to two ligands from the well known cyclopentadienyl (Cp) family of ligands such as pentamethylcyclopentadienyl, indenyl, or fluorenyl, were introduced during the last two decades for the purpose of catalytic polymerization of alpha-olefin monomers. The most common type of metallocene pre-catalyst is a neutral complex including a metal in oxidation state of +4, bound to two anionic ligands in addition to two standard Cp ligands, for example, bis(cyclopentadienyl)titanium dichloride, also known as titanocene dichloride. A related group of complexes is ‘constrained geometry’ pre-catalysts, featuring a metal bound to both a single Cp type ligand and a second anionic group, where the Cp ligand and second anionic group are covalently linked.
Using metallocene and metallocene type pre-catalysts in catalytic processes and systems for polymerization of alpha-olefin monomers affords better control of molecular weight and narrower molecular weight distribution, translating to lower values of PDI, relative to the classical Ziegler-Natta family of pre-catalysts such as titanium trichloride using a trialkyl-aluminum co-catalyst. Metallocene and metallocene type pre-catalysts, processes, and systems are well known and taught about in the art. These pre-catalysts, processes and systems are, however, limited in many respects relating to the above discussion.
Foremost, with respect to catalytic activity, metallocene type pre-catalysts typically exhibit relatively moderate activity for polymerizing a small variety of alpha-olefin monomers. With respect to poly(alpha-olefin) product types and variety, alpha-olefin monomers polymerized by metallocene pre-catalysts are mostly short chain ethylene and propylene, which are already well taught about. Metallocene pre-catalysts are limited in terms of availability and versatility. With respect to pre-catalyst availability, metallocene type pre-catalysts are relatively difficult to synthesize, a fact which affects the possibility of developing new varieties of metallocene type alpha-
Goldschmidt Zeev
Kol Moshe
Tshuva Edit
Rabago R.
Ramot University Authority for Applied Research and Industrial D
Wu David W.
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