Zwitterionic polymerization catalyst

Details Zwitterionic polymerization catalyst Zwitterionic polymerization catalyst

2000-02-11

2002-10-15

Wu, David W. (Department: 1713)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Organic compound containing

C526S133000, C526S134000, C526S160000, C526S943000

Reexamination Certificate

active

06465385

ABSTRACT:

TECHNICAL FIELD
The present invention is a new class of olefin polymerization catalysts, and methods of making the same. These new catalysts are characterized in that they are comprised of Zwitterions with significant dipole moments. Active site ion pairs are thus optimally formed of component ionic (one anionic and one cationic) moieties from different (Zwitteonic) molecules. During polymerizations that occur in nonpolar media the active species (i.e. ion pairs) become uniformly dispersed inside the polymer particles formed, while the length of the spacers separating the positive from the negative end of every Zwitterion increase as a consequence of the polymerization on the active metal-carbon bond of the catalyst.
BACKGROUND OF THE INVENTION
Metallocene catalysis is a relatively new field in the art of olefinic polymerization and provides homogeneous catalysts promoting ethylene polymerization as well as &agr;-olefin polymerization to polymers of controlled structure (e.g. isotactic or syndiotactic polypropylene).
Traditional metallocene catalysts, as well as their manufacture are illustrated in the following prior art documents, which prior art documents are hereby incorporated by reference:
U.S. Pat. No. 4,542,199 describes the use of dihalo- and hydrocarbyl, halometallocenes with alumoxanes. U.S. Pat. No. 4,841,004 discloses a specific type of substituted metallocene to give 1-olefin stereoblock polymer. U.S. Pat. No. 5,091,352 describes various acceptable aluminum compounds suitable for use as cocatalysts with metallocenes and polymerization processes in the presence of isobutene.
U.S. Pat. No. 5,153,157 illustrates how the prior art references comprise a large non-limiting list of acceptable metallocene compounds which function in 1-olefin polymerization as well as the general use of large non-coordinating anionic cocatalytic components which is generally acknowledged to be one essential role of the alumoxane cocatalyst. U.S. Pat. No. 5,416,179 describes at least one non-alumoxane cocatalyst and a process for the polymerization of mono-1-olefins with metallocenes. U.S. Pat. No. 5,480,848 describes metallocene cocatalyst compositions containing acidic hydrogen free boron compounds with organoaluminoxy compounds.
One of the earliest descriptions of the metallocene methyl alumoxane (MAO) catalysts is found in the book “Transition Metal Catalyzed Polymerizations Alkenes and Dienes Part A” edited by Roderic P. Quirk et al., published for MNI Press by Harwood Academic Publishers, Chur, London, New York, specifically, an article entitled “Polymerization and Copolymerization with a Highly Active, Soluble Ziegler-Natta Catalyst” by Walter Kaminsky which begins on page 225 therein.
Prior art metallocene catalysts are either unsupported or supported The former catalysts are generally soluble in the reaction media of choice and lead to small polymer particles with uncontrolled morphologies. This is a limitation which makes polymer disengagement from the reaction medium more difficult than the previous generation of olefin polymerization catalysts which are the current norm. Other aspects of downstream processing are also more difficult.
Supporting metallocene catalysts overcome some of these process limitations, but introduce other complicating factors, such as the introduction of the supporting material which dilutes the active species and contributes potentially deleterious impurities to the final polymer. The supporting process may also perturb the active catalyst species, possibly reducing activity or altering the micro-structure of the polymer produce.
Therefore, it is the objective of the present invention to provide a catalyst promoting polymerization of ethylene and alpha olefins to isotactic, syndiotactic, predominantly isotactic or predominantly syndiotactic polymers which overcomes the limitations imposed by the prior technology. The tacticity of the polymer produced depends on the structure of the transition metal containing moiety, and so other tacticities to these are also possible. Even though the catalyst is not supported, granular polymer particles which are expected to be easily separated from the reaction medium can be formed. This polymer will be absent added impurities which supported materials would have added. An added improvement would be the process simplification attendant in not needing a cocatalyst.
Another objective of the present invention is to provide methods of making the catalysts of the present invention.
A further object of the present invention is to provide a method of using the catalysts of the present invention to catalyze polymerization reactions including the catalyst material and/or &agr;-olefins.
SUMMARY OF THE INVENTION
The present invention relates to novel high dipole moment Zwitterionic metallocene catalysts which form by isomerization of an initially formed ionic metallocene catalyst. These catalysts comprise, an ionic pair shown below as (I). With the exception of the R
I
, group (shown in I below), formula I is similar to known catalysts. The R
I
group is not expected to interfere with catalyst activity other than allowing an isomerizing olefin insertion onto the metal carbon bond. Because of this isomerization the specific zwitterionic compounds of this invention are formed. Thus, these catalysts are shown in the following formula (I) and via the above noted isomerization are derived from one or more ionic pairs having the following formulae:
[(X)
x
MR
3−x
]
+−
[(X
I
)
w
—B—[(X
II
)
y
—(C
n
H
m
)—R
I
)]
4−w
]  (I)
wherein,
[(X)
x
MR
3−x
]
+
designates any of the innumerable metallocene derived cationic active sites many examples of which can be found in the patents and literature generally and as cited above.
In these compounds X designates an organic moiety which contains a cyclopentadienyl, substituted cyclopentadienyl or other structure, as is commonly known in the art, which imparts the general designation “metallocene” and provides the bond of the X moiety to the metal “M.” This moiety may be a unitary structure (x=1) in which case it may consist of, for example, one cyclopentadienyl containing structure. When x is 2, it may consist of two cyclopentadienyl or substituted cyclopentadienyl containing structures. These two cyclopentadienyl or substituted cyclopentadienyl moieties can be connected via a suitable bridge such as dimethylsilyl, diphenylsilyl, isopropylidene, 1,2ethanediyl, etc. Therefore, x is either 1 or 2 and indicates the number of expected metalcyclopentadienyl bonds.
R is a hydrocarbyl moiety. When attached to M (see below), it is preferably methyl. M is a metal usually selected from Ti, its congeners in Group IVB and the metals in the periodic table close to it including Group VB and VIB metals. Preferably, M is a transition Group IVB metal and most preferably Zr.
The
−
[(X
I
)
w
—B—[(X
II
)
y
—(C
n
H
m
)—R
I
)
4−w
]] substructure represents a subset of all possibilities which define the unique portion of what has been found and described herein R
I
,is a terminal olefinic moiety. When n is not equal to 0 and m is not equal to 0 minimally it is —CH═CH
2
or if n=m=0 minimally it is —CH
2
—CH═CH
2
.
B is selected from Group IIIA, and is preferably Boron.
X
I
is a large electron withdrawing group, as is known in the art, preferably pentafluorophenyl (C
6
F
5
). The R
I
moiety is connected to boron optionally through X
II
which is a proper spacer, for example O or NR (R as above).
C
n
H
m
is a connecting hydrocarbyl moiety with a and m chosen within the laws of valency, n is ≧0. If n=0, then m=0. Otherwise m≧0. For purposes of economy from here on the (C
n
H
m
) moiety win be abbreviated “CH.”
Additionally, w is 2 or 3 and y is 0 or 1.
The ionic pairs of the present invention are capable of reacting with the unsaturations of R
I
that is converted to R
II
(see below). Due to their high dipole moment the Zwitterionic pairs (exemplified below

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