Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-06-25
2003-10-14
Harlan, Robert (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S161000, C526S172000, C526S133000, C526S348500, C526S905000, C502S155000, C502S167000, C556S056000
Reexamination Certificate
active
06632899
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to catalytic polymerization, in general, and, tactic catalytic polymerization, in particular, of alpha-olefin monomers using an active non-metallocene pre-catalyst featuring a diamine diphenolate complex, and a corresponding method using the disclosed 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. In general, 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 functions in concert with at least one co-catalyst for effecting catalytic polymerization of an alpha-olefin monomer. It is noted, however, that there are rare exceptions of a particular pre-catalyst functioning without first being activated by a 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, tactic polymers made from alpha-olefin monomers featuring more than two carbon atoms, having well defined bulk or global physicochemical properties, such as mechanical strength, elasticity, melting point, and chemical resistance, applicable for manufacturing a diversity of end products. This may be achieved by controlling the polymer tacticity and 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.
Bulk or global physicochemical properties of polymers are directly related to, and are controllable by, molecular or local physicochemical characteristics of the polymer units making up the bulk polymer. Three notable molecular physicochemical characteristics are polymer molecular weight, polymer molecular weight distribution, and polymer tacticity.
Polymer molecular weight and polymer molecular weight distribution 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 polymer chains 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, and the rate of termination reactions is negligible relative to propagation. 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.
Another current challenge in the field of catalytic polymerization of alpha-olefins is to design alpha-olefin polymerization pre-catalysts, and catalytic systems including such pre-catalysts, leading to poly(alpha-olefin) products having controllable and classifiable degrees of polymer tacticity. Polymer tacticity is another very significant molecular physicochemical characteristic of a polymer which can dramatically determine and influence bulk physicochemical properties of a polymer, such as a poly(alpha-olefin) polymer. The term ‘polymer tacticity’ refers to the particular micro- or local structural configuration of the substituents on the polymer backbone, or equivalently, stereo-regularity of the polymer chain, as to whether a polymer is, for example, isotactic, syndiotactic, or, atactic. Polymer tacticity is typically used in reference to a hydrocarbon polymer derived from polymerization of a monomer having more than two carbon atoms, such that the polymer has a side chain on every other carbon atom of the polymer backbone. Moreover, there are different particular forms or types of ‘polymer tacticity’ according to the particular micro- or local structure in terms of the relative orientations of the side chains bound to the polymer backbone.
A polymer in which all the side chains extend or protrude from the same side or plane of the polymer backbone is referred to as an ‘isotactic polymer’ which is obtained from an ‘isotactic’, or equivalently, an ‘isospecific’ polymerization process. A polymer in which the side chains alternately extend or protrude from opposite sides of the polymer backbone is referred to as a ‘syndiotactic polymer’ which is obtained from a ‘syndiotactic’, or equivalently, a ‘syndiospecific’ polymerization process. A polymer in which the side chains randomly extend or protrude from either side of the polymer backbone is referred to as an ‘atactic polymer’, which is obtained from an ‘atactic’ polymerization process. Furthermore, extent or degree of a particular form or type of polymer tacticity is also used in reference to polymer tacticity. For example, a polymer may be classified as being eighty percent isotactic and twenty percent atactic. Another example is a hemi-isotactic polymer, in which every second side chain extends or protrudes from the same side or plane of the polymer backbone, whereas the rest of the side chains randomly extend or protrude from either side of the polymer backbone. Typically, extent or degree of tacticity of a polymer, or a polymerization process, is determined by subjecting the polymer, or products of the polymerization process, to NMR spectroscopic analysis, more particularly,
13
C NMR.
An illustrative example showing the dramatic influence polymer tacticity
Kol Moshe
Tshuva Edit Y.
G.E. Ehrlich (1995) Ltd.
Harlan Robert
Ramot at Tel Aviv University Ltd.
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