Polymers from ionic metallocene catalyst compositions

Details Polymers from ionic metallocene catalyst compositions Polymers from ionic metallocene catalyst compositions

1998-12-30

2001-05-15

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...

C526S351000, C526S348500, C526S335000, C526S337000, C526S133000, C526S160000, C526S943000, C502S152000, C502S203000

Reexamination Certificate

active

06232420

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to catalyst compositions, to a method for preparing such catalyst compositions, to a method of using such catalysts and to products produced with such catalyst compositions. More particularly, this invention relates to compositions, comprising ionic metallocene catalyst compositions which are active to polymerize olefins, diolefins and/or acetylenically unsaturated monomers to homopolymer and copolymer products.
BACKGROUND OF THE INVENTION
Soluble Ziegler-Natta type catalysts for the polymerization of olefins are well known in the art. Generally, these catalysts comprise a Group IV-B metal compound and a metal alkyl cocatalyst, particularly an aluminum alkyl cocatalyst. A subgenus of such catalysts is that wherein the Group IV-B metal component comprises a bis(cyclcpentadienyl) Group IV-B metal compound (i.e. —a “metallocene”), particularly a titanium compound, combination with an aluminum alkyl cocatalyst. While speculation remains concerning the actual structure of the active catalyst species o this subgenus of soluble Ziegler-Natta type olefin polymerization catalysts, it appears generally accepted that the structure of the catalytically active species is a Group IV-B metal cation in the presence of a labile stabilizing anion. This is a theory advocated by Breslow and Newburg, and Long and Breslow, in their respective articles in
J. Am. Chem, Soc.,
1959, Vol. 81, pp. 81-86, and
J. Am. Chem. Soc.,
1960, Vol. 82, pp. 1953-1957. As there indicated, studies have suggested that the catalytically active species is a titanium-alkyl complex or a species derived therefrom when a titanium compound; viz., bis(cyclopentadienyl) titanium dihalide, and an aluminum alkyl are used as a catalyst or catalyst precursor. The presence of ions, all being in equilibrium, when a titanium compound is used was also suggested by Dyachkovskii,
Vysokomol. Soved.,
1965, Vol. 7, pp. 114-115 and by Dyachkovskii, Shilova and Shilov,
J. Polym. Sci.. Part C,
1967, pp. 2333-2339. That the active catalyst species is a cation complex when a titanium compound is used, was further suggested by Eisch et al.,
J. Am. Chem. Soc.,
1985, Vol. 107, pp. 7219-7221.
While the foregoing articles teach or suggest that the active catalyst species is an ion pair wherein the Group IV-B metal component is present as a cation, all of the articles teach the use of a cocatalyst comprising a Lewis acid either to form or to stabilize the active ionic catalyst species. The active catalyst is, apparently, formed through a Lewis acid-Lewis base reaction of two neutral components (the metallocene and the aluminum alkyl), leading to an equilibrium between a neutral catalytically inactive adduct and the active catalyst ion pair. As a result of this equilibrium, there is a competition for the anion which must be present to stabilize the active cation catalyst species. This equilibrium is, of course, reversible and such reversal deactivates the active catalyst species. Further, many, if not all, of the Lewis acids heretofore contemplated for use in soluble Ziegler-Natta type catalyst systems are chain transfer agents and, as a result, prevent effective control of the product polymer molecular weight and molecular weight distribution. Still further, the catalyst systems heretofore proposed do not generally facilitate incorporation of a significant amount of a plurality of different monomers or random distribution of such monomers when used in copolymerization processes, particularly &agr;-olefin copolymerization processes.
The aforementioned metallocene catalyst systems are not highly actiwe, nor are they generally active when the Group IV-B metal is zirconium or hafnium. More recently, however, active Zeaier-Natta type catalysts have been found which are formed when bis(cyclopentadienyl) compounds of the Group IV-B metals, including zirconium and hafnium, are combined with alumoxanes. As is well known, these systems, particularly those employing a zirconocene, offer several distinct advantages, including much higher activities than the aforementioned bis(cyclopentadienyl) titanium catalysts and the production of polymers with narrower molecular weight distributions than those from conventional Ziegier-Matta catalysts. Achiral bis(cyclopentadienyl)hafnium compounds, hafnocenes, used with alumoxane cocatalysts have offered few, if any, advantages when compared to analogous titanocenes or zirconocenes with respect to catalyst activity, polymer molecular weights, or extent or randomness of comonomer incorporation. Giannetti, Nicolett, and Mazzochi,
J. Polym. Sci. Polym. Chem.,
1985, Vol. 23, pp. 2117-2133, claim that the ethylene polymerization rates of hafnocenes are five to ten times slower than those of similar zirconocenes while there is little difference between the two metallocenes in the molecular weight of the polyethylene formed from them. European Patent Application No. 200,351 A2 (1986) suggests that in the copolymerization of ethylene and propylene, there is little difference between titanocenes, zirconocenes and hafnocenes either in polymer molecular weights and molecular weight distributions or in ability to incorporate propylene randomly. Recently, however, Ewen et al. disclosed in
J. Am. Chem. Soc.,
1987, Vol. 109, pp. 6544-6545, that chiral hafnocenes used wath an alumoxane cocatalyst give isotactic polypropylene of higher molecular weight than that obtained from analogous chiral zirconocenes. In light of the deficiencies of the metallocene catalyst systems heretofore contemplated, a need still exists for an improved metallocene catalyst system which: (1) permits better control of polymer product's molecular weight and molecular weight distribution.; (2) is not subject to activation equilibrium, and (3) does not require the use of an undesirable excess of the cocatalyst. The need for a catalyst system which will facilitate the production of higher molecular weight polymeric products and facilitate incorporation of a larger amount of comonomer into a copolymer is also believed to be readily apparent.
SUMMARY OF THE INVENTION
This invention provides improved ionic metallocene catalyst compositions which are useful in the polymerization of olefins, diolefins and/or acetylenically unsaturated monomers. This invention provides a method for preparing such improved catalyst compositions. The improved catalysts are not subject to ion equilibrium reversal deactivation and permit better control of the product polymer molecular weight and molecular weight distribution. The improved catalysts, particularly certain hafnium containing catalysts, yield relatively high molecular weight polymers, yield copolymers containing relatively large amounts of a plurality of comonomers which are also distributed in a manner at least approaching randomness, and provide polymeric products having relatively narrow molecular weight distributions.
The catalyst composition comprises a Group IV-B metal cation and a non-coordinating anion, which composition is represented by one of the general formulae:
1. {[(A—Cp)MX
1
]
+
}d[B′]
d−
2. {[(A—Cp)MX
5
L′]
+
}
d
[B′]
d−
wherein:
(A—Cp) is either (Cp) (Cp′) or Cp—A′—Cp′; Cp and Cp′ are the same or different cyclopentadienyl rings substituted with from zero to five substituent groups S, each substituent group S being, independently, a radical group which is a hydrocarbyl, substituted-hydrocarbyl, halocarbyl, substituted-halocarbyl, hydrocarbyl-substituted organometalloid, halocarbyi-substituted organometalloid and halogen radicals or Cp and Cp′′ are cyclopentadienyl rings in which any two adjacent S groups are joined forming a C
4
to C
20
ring to give a saturated or unsaturated polycyclic cyclopentadienyl ligand; and A′ is a bridging group restricting rotation of the Cp and Cp′ rings;
M is titanium, zirconium or hafnium;
L′ is a neutral Lewis base;
X
1
is a hydride radical, hydrocarbyl radical, subs

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