Catalyst system

Details Catalyst system Catalyst system

2000-07-13

2002-11-19

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...

C526S129000, C526S132000, C526S134000, C526S139000, C526S141000, C526S151000, C526S153000, C526S160000, C502S117000, C502S121000, C502S123000, C502S132000

Reexamination Certificate

active

06482902

ABSTRACT:

The present invention describes a catalyst system comprising metallocene, cocatalyst, support material and, if desired, further organometallic compounds. The catalyst system can advantageously be used for the polymerization of olefins, where the use of aluminoxanes such as methylaluminoxane (MAO), which usually has to be used in a large excess, as cocatalyst can be dispensed with and a high catalyst activity and good polymer morphology are nevertheless achieved.
The role of cationic complexes in Ziegler-Natta polymerization using metallocenes is generally recognized (H. H. Brintzinger, D. Fischer, R. Mülhaupt, R. Rieger, R. Waymouth, Angew. Chem. 1995, 107,1255-1283).
The preparation of such cationic alkyl complexes opens up the possibility of obtaining MAO-free catalysts having comparable activity; in this case the cocatalyst can be used in a virtually stoichiometric amount.
The synthesis of “cation-like” metallocene polymerization catalysts is described in J. Am. Chem. Soc. 1991, Volume 113, page 3623.
A process for preparing salts of the formula LMX
+
XA
−
by the above-described principle is claimed in EP-A-0,520,732.
EP-A-0,558,158 describes zwitterionic catalyst systems which are prepared from dialkylmetallocene compounds and salts of the formula [R
3
NH]
+
][B(C
6
H
5
)
4
]
−
. The reaction of such a salt with, for example, CP
2
ZrMe
2
gives, as a result of protolysis with elimination of methane, a methylzirconocene cation as intermediate. This reacts further via C—H activation to give the zwitterion Cp
2
Zr
+
-(m-C
6
H
4
)-BPh
3
−
. Here, the Zr atom is covalently bound to a carbon atom of the phenyl ring and is stabilized by means of agostic hydrogen bonds. U.S. Pat. No. 5,348,299 describes zwitterionic catalyst systems which are prepared from dialkylmetallocene compounds and salts of the formula [R
3
NH]
+
[B(C
6
F
5
)
4
]
−
by protolysis. The C—H activation as subsequent reaction does not occur here.
EP-A-0,426,637 utilizes a process in which the Lewis-acid CPh
3
+
cation is used for abstracting the methyl group from the metal center. B(C
6
F
5
)
4
−
likewise functions as a weakly coordinating anion.
Industrial utilization of metallocene catalysts requires the catalyst system to be made heterogeneous in order to achieve an appropriate morphology of the resulting polymer. The application of cationic metallocene catalysts based on the abovementioned borate anions to a support is described in WO-91/09882. Here, the catalyst system is formed by applying a dialkylmetallocene compound and a Brönsted acid, quaternary ammonium compound containing a non-coordinating anion such as tetrakispentafluorophenylborate to an inorganic support. The support material is modified beforehand by means of a trialkylaluminum compound. A disadvantage of this method of applying the catalyst to a support is that only a small proportion of the metallocene used is fixed to the support material by physisorption. When the catalyst system is metered into the reactor, the metallocene can easily become detached from the support surface. This leads to a partially homogeneous polymerization which results in an unsatisfactory polymer morphology.
WO-96/04319 describes a catalyst system in which the cocatalyst is covalently bound to the support material. However, this catalyst system has a low polymerization activity and, in addition, the high sensitivity of the supported cationic metallocene catalysts can lead to problems in introducing them into the polymerization system.
It would therefore be desirable to develop a catalyst system which may either be activated before introduction into the reactor or be activated only in the polymerization autoclave.
It is therefore an object of the invention to provide a catalyst system which avoids the disadvantages of the prior art and nevertheless guarantees high polymerization activities and a good polymer morphology. A further object of the invention is to develop a process for preparing this catalyst system, which process makes it possible for the activation of the catalyst system to be carried out either before introduction into the reactor or else only after it has been introduced into the polymerization autoclave.
The present invention provides a supported catalyst system and provides for its use in the polymerization of olefins.
The catalyst system of the invention comprises
a) at least one metallocene,
b) at least one Lewis base of the formula I,
M
2
R
3
R
4
R
5
  (I)
 where
R
3
, R
4
and R
5
are identical or different and are each a hydrogen atom, a C
1
-C
20
-alkyl group, C
1
-C
20
-haloalkyl group, C
6
-C
40
-aryl group, C
6
-C
40
-haloaryl group, C
7
-C
40
-alkylaryl group or C
7
-C
40
-arylalkyl group, where two radicals or all three radicals R
3
, R
4
and R
5
may be connected to one another via C
2
-C
20
-units, and
M
2
is an element of main group V of the Periodic Table of the Elements,
c) a support,
d) at least one organoboroaluminum compound which is built up of units of the formula II
R
i
1
M
3
—O—M
3
R
j
2
  (II)
 where
R
1
and R
2
are identical or different and are each a hydrogen atom, a halogen atom, a C
1
-C
40
-group, in particular C
1
-C
20
-alkyl, C
1
-C
20
-haloalkyl, C
1
-C
10
-alkoxy, C
6
-C
20
-aryl, C
6
-C
20
-haloaryl, C
6
-C
20
-aryloxy, C
7
-C
40
-arylalkyl, C
7
-C
40
-haloarylalkyl, C
7
-C
40
-alkylaryl or C
7
-C
40
-haloalkylaryl, or R
1
is an —OSiR
3
group, where R are identical or different and are as defined for R
1
,
M
3
are identical or different and are each an element of main group III of the Periodic Table of the Elements and
i and j are each an integer 0, 1 or 2,
and is covalently bound to the support, and, if desired,
e) an organometallic compound of the formula V
[M
4
R
6
p
]
k
  (V)
 where
M
4
is an element of main group I, II or III of the Periodic Table of the Elements,
R
6
are identical or different and are each a hydrogen atom, a halogen atom, a C
1
-C
40
-group, in particular C
1
-C
20
-alkyl, C
6
-C
40
-aryl, C
7
-C
40
-arylalkyl or C
7
-C
40
-alkylaryl,
p is an integer from 1 to 3 and
k is an integer from 1 to 4.
The Lewis bases of the formula (I) are preferably ones in which M
2
is nitrogen or phosphorus. Examples of such compounds are triethylamine, triisopropylamine, triisobutylamine, tri(n-butyl)amine, N,N-dimethylaniline, N,N-diethylaniline, N,N-2,4,6-pentamethylaniline, dicyclohexylamine, pyridine, pyrazine, triphenylphosphine, tri(methylphenyl)phosphine and tri(dimethylphenyl)phosphine.
The support is a porous inorganic or organic solid. The support preferably comprises at least one inorganic oxide such as silicon oxide, aluminum oxide, aluminosilicates, zeolites, MgO, ZrO
2
, TiO
2
, B
2
O
3
, CaO, ZnO, ThO
2
, Na
2
CO
3
, K
2
CO
3
, CaCO
3
, MgCO
3
, Na
2
SO
4
, Al
2
(SO
4
)
3
, BaSO
4
, KNO
3
, Mg(NO
3
)
2
, Al(NO
3
)
3
, Na
2
O, K
2
O or
Li
2
O, in particular silicon oxide and/or aluminum oxide.
The support can also comprise at least one polymer, e.g. a homopolymer or copolymer, a crosslinked polymer or polymer blend. Examples of polymers are polyethylene, polypropylene, polybutene, polystyrene, divinylbenzene-crosslinked polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyamide, polymethacrylate, polycarbonate, polyester, polyacetal or polyvinyl alcohol.
The support has a specific surface area in the range from 10 to 1000 m
2
/g, preferably from 150 to 500 m
2
/g. The mean particle size of the support is from 1 to 500 &mgr;m, preferably from 5 to 350 &mgr;m, particularly preferably from 10 to 200 &mgr;m.
The support is preferably porous with a pore volume of from 0.5 to 4.0 ml/g of support, preferably from 1.0 to 3.5 ml/g. A porous support has a certain proportion of voids (pore volume). The pores are usually irregular in shape, frequently spherical. The pores can be interconnected by small pore openings. The pore diameter is preferably from about 2 to 50 nm. The particle shape of the porous support de

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