Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
2000-07-14
2002-07-16
Wu, David W. (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S152000, C526S133000, C526S160000, C526S161000, C526S171000, C526S943000
Reexamination Certificate
active
06420300
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a catalyst system for the preparation of olefin copolymers. The catalyst system is especially useful for the preparation of ethylene copolymers which have very high molecular weight and very low density. The catalyst system is characterized by the use of an organometallic complex having a ketimide ligand.
BACKGROUND OF THE INVENTION
Ketimide complexes of group 4 metals have been reported in the literature—see, for example, the review of titanium chemistry which as prepared in part by one of us in 1982 (Ref: M. Bottrill, P. D. Gavens, J. W. Kelland and J. MeMeeking in “Comprehensive Organometallic Chemistry”, Ed. G. Wilkinson, F. G. A. Stone, & E. W. Abel, Pergamon Press, 1982, Section 22.3, page 392). However, the use of ketimide ligand/group 4 metal complex as an ethylene polymerizafion catalyst was heretofore unknown.
Preferred ketimide catalysts of this invention also contain one and only one cyclopentadienyl-type ligand.
The prior art includes many examples of olefin polymerization catalysts having a single cyclopentadienyl ligand—most notably the so called Bercaw ligand (*Cp-Me
2
Si—N
t
Bu) which was disclosed as a Scandium complex by Bercaw et al In the fall of 1988 and subsequently claimed as a titanium complex in U.S. Pat. No. 5,064,802 (Stevens and Neithamer, to Dow Chemical) and U.S. Pat. No. 5,055,438 (Canich, to Exxon). The use of a titanium complex of the Bercaw ligand provides an olefin polymerization catalyst which has excellent commoner response—i.e. the catalyst Is excellent for the preparation of ethylene/&agr;-olefin copolymers. However, the bridged structure of the Bercaw ligand is expensive to synthesize. Accordingly, an olefin polymerization catalyst which doesn't require a “bridge” to provide commoner response would represent a useful addition to the art.
SUMMARY OF THE INVENTION
The present invention also provides a catalyst system for olefin polymerization comprising;
(a) a catalyst which is an organometallic complex of a group 4 metal; and
(b) an activator, characterized in that such organometallic complex contains a ketimide ligand.
Preferred forms of the catalyst contain a single ketimide ligand and a single cyclopentadienyl-type ligand.
The invention further provides a process for the copolymerization of ethylene with at least one other olefin monomer using the above described catalyst system.
DETAILED DESCRIPTION
The term “group 4” metal refers to conventional IUPAG nomenclature. The preferred group 4 metals are Ti, Hf and Zr with Ti being most preferred.
As used herein, the term “ketimide ligand” refers to a ligand which:
(a) is bonded to the group 4 metal via a metal-nitrogen atom bond,
(b) has a single substituent on the nitrogen atom, (where this single substituent Is a carbon atom which is doubly bonded to the N atom); and.
(c) has two substituents (Sub 1 and Sub 2, described below) which are bonded to the carbon atom.
Conditions a, b, and c are illustrated below:
The substituents “Sub 1 and Sub 2” may be the same or different. Exemplary substituents include hydrocarbyls having from 1 to 20 carbon atoms; silyl groups, amido groups and phosphido groups. For reasons of cost and convenience it is preferred that these substituents both be hydrocarbyls, especially simple alkyls and most preferably tertiary butyl.
In the preferred catalyst systems, the catalyst is defined by the formula:
L
1
L
2
MX
2
formula 1
L2:
L2 is a cyclic ligand which forms a delocalized pi-bond with the group 4 metal. L2 is preferably a cyclopentadienyltype ligand.
As used herein, the term cyclopentadienyl-type is meant to convey its conventional meaning and to include indenyl and fluorenyl ligands. The simplest (unsubstituted) cyclopentadione indeno and fluorene structures are illustrated below.
Ligands in which one of the carbon atoms in the ring is replaced with a phosphorous atom (i.e. a phosphole) may also be employed
It will be readily appreciated by those skilled in the art that the hydrogen atoms shown in the above formula may be replaced with substituents to provide the “substituted” analogues, Thus, the preferred catalysts contain a cyclopentadienyl structure which may be an unsubstituted cyclopentadienyl, substituted cyclopentadienyl, unsubstituted indenyl, substituted indenyl, unsubstituted fluorenyl or substituted fluorenyl. A description of permissible substituents on these cyclopentadienyl-type structures is provided in U.S. Pat. No. 5,324,800 (Welbom).
An illustrative list of such substituents for cyclopentadienyl groups included C
1
-C
20
hydrocarbyl radicals; substituted C
1
-C
20
hydrocarbyl radicals wherein one or more hydrogen atoms is replaced by a halogen radical, an amido radical, a phosphido radical, an alkoxy radical or a radical containing a Lewis acidic or basic functionality; substituted C
1-C
20
hydrocarbyl radicals wherein the substituent contains an atom selected from the group 14 of the Periodic Table of Elements (where group 14 refers to IUPAC nomenclature); and halogen radicals, amido radicals, phosphido radicals, alkoxy radicals, alkyborido radicals, or a radical containing Lewis acidic or basic functionality; or a ring in which two adjacent R-groups are joined forming C
1-C
20
ring to give a saturated or unsaturated polyclinic ligand.
Ligand X: “Non-Interfering Anionic Ligand”
Referring for formula 1, the preferred catalyst systems according to this invention contain two simple anionic ligands denoted by the letter X.
Any simple anionic ligand which may be bonded to an analogous metallocene catalyst component ((i.e. where the analogous metallocene catalyst component is defined by the formula Cp
2
M(X)
2
, where Cp is a cyclopentadienyl-type ligand; M Is a group 4 metal; and X is a non-interfering ligand Is previously defined herein) may also be used with the catalyst components or this invention.
“Non-interfering” means that this ligand doesn't interfere with (deactivate) the catalyst.
An Illustrative list includes hydrogen, hydrocarbyl having up to 10 carbon atoms, halogen, amido and phosphido (with each X preferably being chlorine, for simplicity).
Polymerization Details
The polymerization process of this invention is conducted in the presence of a catalyst and an “activator or cocatalyst”. The terms “activator” or “cocatalyst” may be used interchangeably and refer to a catalyst component which combines with the organometallic complex to form a catalyst system that is active for olefin polymerization.
Preferred cocatalysts are the well know alumoxane (also known as aluminoxane) and ionic activators.
The term “alumoxane” refers to a well known article of commerce which is typically represented by the following formula:
R
2
′AlO(R′AlO)
m
AlR
2
′
were each R′ is independently selected from alkyl, cycloalkyl, aryl or alkyl substituted aryl and has from 1-20 carbon atoms and where m is from 0 to about 50 (especially from 10 to 40). The preferred alumoxane is methylalumoxane or “MAO” (where each of the R′ is methyl).
Alumoxanes are typically used in substantial molar excess compared to the amount of metal in the catalyst. Aluminum:transition metal molar ratios of from 10:1 to 10,000:1 are preferred, especially from 50:1 to 500:1.
Another type of activator is the “ionic activator” or “substantially non-coordinating anion”. As used herein, the term substantially non-coordinating anions (“SNCA”) well known cocatalyst or activator systems which are described, for example, in U.S. Pat. No. 5,153,157 (Hlatky and Turner), and the carbonium, sulfonium and oxonium analogues of such activators which are disclosed by Ewen in U.S. Pat. No. 5.387.568. In general, these SNCA form an anion which only weakly coordinates to a cationic form of the catalyst.
While not wanting to be bound by theory, it is generally believed that SNCA-type activators ionize the catalyst by abstraction or protonation of one of the “X” ligands (non-interfering ligands) so as to ionize the group 4 metal center into a cation (but not to covalently bond with the group 4 metal)
Brown Stephen John
Gao Xiaoliang
Jeremic Dusan
McMeeking John
Spence Rupert Edward von Haken
Harlan R.
Johnson Kenneth H.
Nova Chemicals (International) S.A.
Wu David W.
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