Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
2001-02-22
2003-08-19
Wu, David W. (Department: 1713)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C556S053000, C526S127000, C526S134000, C526S160000, C526S161000, C526S943000, C526S157000, C502S103000, C502S117000, C502S152000, C502S155000
Reexamination Certificate
active
06608224
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to organometallic compounds a to catalyst systems for the polymerization of olefins comprising such organometallic compounds. The invention also relates to a process for the polymerization of olefins carried out in the presence of the above catalyst system.
PRIOR ART DISCLOSURE
Homogeneous catalytic systems based on metallocene complexes are known to be active in the polymerization of olefins; said complexes must be activated by means of suitable cocatalytic compounds.
The first generation of cocatalysts developed for homogeneous metallocene olefin polymerization consisted of alkyl aluminum chlorides (AlR
5
Cl), wherein substituents R are preferably methyl or ethyl; these cocatalysts exhibit low ethylene polymerization activity levels and negligible propylene polymerization activity.
The second generation of cocatalyst systems comprised the class of alkylalumoxanes, commonly obtained by reacting trialkyl aluminum compound and water in a molar ratio of 1:1 to 100:1; these alumoxanes are oligomeric linear and/or cyclic compounds represented by the formulae:
for linear oligomeric alumoxanes, and
for cyclic oligomeric alumoxanes, wherein the substituents R are usually methyl, ethyl or isobutyl groups, n ranges from 0 to 40, and m ranges from 3 to 40. Methylalumoxane (MAO) is the most widely used cocatalyst.
Nevertheless alkylalumoxanes, and in particular methylalumoxane, though very active in metallocene-based catalyst systems, exhibit several inherent problems in use, such as the need for high alumoxane/metallocene molar ratios to produce satisfactory catalytic activities, their high reactivity toward impurities (moisture, alcohols etc.) and their easy flammability. Moreover, it has not been possible to isolate characterizable metallocene active species using MAO. Accordingly, some of the developments in this area involved a search for alternative cocatalysts. B(C
6
F
5
)
4
−
types of non-coordinating anions have been developed as cocatalysts for metallocene-based systems. More specifically, these activators are ion-exchange compounds comprising a trialkyl or dialkylammonium cation, which will irreversibly react with a metallocene, and a fluorinated arylborate anion, capable of stabilizing the metallocene cation complex and sufficiently labile to permit displacement by ethylene during polymerization (see for instance WO 91/02012). In particular, they have the advantage of being used in a 1:1 catalyst-cocatalyst ratio. Therefore, it is usually not necessary to remove the small amount of boron from the final polymer, unlike the aluminum-based cocatalysts mentioned above. As preferred activators are tri(n-butyl)ammonium tetrakis(pentafluorophenyl)boron and N,N-dimethylanilinium tetrakis(pentafluorophenyl)boron.
These cocatalysts exhibit high catalytic activities but, from a synthetic point of view, the industrial production of these cocatalysts is quite expensive.
Finally, these B(C
6
F
5
)
4
−
anions are generally used in the form of the corresponding ammonium salts, thus leading to the release of aminic by-products in consequence of the metallocene activation. In addition they have a low solubility in the polymerization solvents.
The fourth generation of cocatalysts is B(C
6
F
5
)
3
. The anion MeB(C
6
F
5
)
3
−
formed after Me
−
abstraction from the metallocene dimethyl complex is weakly coordinated to the electrondeficient metal center, thus resulting in a decrease of the catalytic activity and in addition the catalyst system is not stable.
An alternative route for using B(C
6
F
5
)
3
has been proposed by B. Temme in Journal of Organometallic Chemistry 488 (1995) 177-182. Bis cyclopentadienyl methyl pyrrolidyl zirconocene has been treated with B(C
6
F
5
)
3
with the formation of the pyrrolydyl borate and the metallocene cation. In this paper it is reported that the obtained salt is catalytically active and polymerizes ethylene even if with a moderate activity.
WO 99/64476 describes a process for the preparation of polyolefins by using a catalyst system comprising a metallocene compound, a Lewis acid-base complex and a tri-n-alkylaluminum compound. As described at page 4 and illustrated in the figures the function of the Lewis base is to inhibit the reaction between the metallocene compounds and the Lewis acid. Only upon addition of the tri-n-alkylaluminum compound the catalyst system becomes active. This catalyst system does not solve completely the problems of the use B(C
6
F
5
)
3
, for the reason that the anion that is weakly coordinated to the electrondeficient metal center is always of the type MeB(C
6
F
5
)
3
−
and therefore the active catalyst system is not stable for a long time.
Therefore, there is still the need for alternative cocatalysts, easy to prepare, that form a stable catalyst system and able to exert good activities in the polymerization of olefins.
The Applicant has now found a new class of olefin polymerization cocatalysts, which reduces the use of excess of cocatalyst with respect to alkylaluminoxanes, does not lead to the release of undesired by-products after the metallocene activation, and provides stable catalytic compositions.
The present invention concerns an organometallic compound obtainable by contacting
a) a compound having the following formula (I):
wherein R
a
, R
b
, R
c
and R
d
equal to or different from each other are selected from the group consisting of hydrogen, halogen, linear or branched, saturated or unsaturated, C
1
-C
10
alkyl, C
6
-C
20
aryl, C
7
-C
20
arylalkyl and C
7
-C
20
alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms, or two or more adjacent substituents R
a
, R
b
, R
c
and R
d
form one or more C
4
-C
7
rings, optionally containing O, S, N, P or Si atoms, that can bear substituents; with
b) a Lewis acid of formula (II)
MtR
1
3
(II)
wherein Mt is a metal belonging to Group 13 of the Periodic Table of the Elements (IUPAC); R
1
, equal to or different from each other, are selected from the group consisting of halogen, halogenated C
6
-C
20
aryl and halogenated C
7
-C
20
alkylaryl groups; two R
1
groups can also form with the metal Mt one condensed ring, such as for example 9-borafluorene compounds.
Preferably Mt is B or Al, and more preferably is B; The substituents R
1
are preferably selected from the group consisting of C
6
F
5
, C
6
F
4
H, C
6
F
3
H
2
, C
6
H
3
(CF
3
)
2
, perfluoro-biphenyl, heptafluoro-naphthyl, hexafluoro-naphthyl and pentafluoro-naphthyl; Most preferred R
1
substituents are C
6
F
5
radicals.
Preferred organometallic compounds are those belonging to the following two classes (1) and (2), having respectively formula (III) and (IV).
Class (1)
Organometallic compounds belonging to class (1) have the following formula (III)
wherein
Mt is a metal belonging to Group 13 of the Periodic Table of the Elements (IUPAC); R
1
, equal to or different from each other, are selected from the group consisting of halogen, halogenated C
6
-C
20
aryl and halogenated C
7
-C
20
alkylaryl groups; two R
1
groups can also form with the metal Mt one condensed ring, such as for example 9-borafluorene compounds; and the substituents R
5
, R
4
, R
3
and R
2
equal to or different from each other, are selected from the group consisting of hydrogen, halogen, linear or branched, saturated or unsaturated, C
1
-C
10
alkyl, C
6
-C
20
aryl, C
7
-C
20
arylalkyl and C
7
-C
20
alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms, or two or more adjacent substituents R
2
-R
5
form one or more C
4
-C
7
rings, optionally containing O, S, N, P or Si, preferably when the substituents R
2
-R
5
form one or more rings, R
4
and R
5
form one C
4
-C
7
aromatic ring, optionally containing O, S, N, or P atoms, that can bear substituents; and R
2
and R
3
form one non aromatic C
4
-C
7
ring, optionally containing O, S, N, P or Si atoms; with the proviso that at least one of R
2
, R
3
, R
4
and R
5
is different from hydrogen.
Preferably in the organometallic compounds of formula (II
Guidotti Simona
Resconi Luigi
Basell Polyolefine GmbH
Harlan R.
Wu David W.
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