Metallocene capable of being used for the process for the...

Details Metallocene capable of being used for the process for the... Metallocene capable of being used for the process for the...

1995-06-05

2004-03-30

Choi, Ling-Siu (Department: 1713)

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

Catalyst or precursor therefor

Organic compound containing

C556S011000, C556S052000, C556S053000

Reexamination Certificate

active

06713426

ABSTRACT:

The invention relates to a novel process, which can be employed on a large industrial scale, for the preparation of a syndiotactic polyolefin.
Syndiotactic polyolefins, in particular syndiotactic polypropylene, are known per se. However, it has not yet been possible to prepare such polymers in an adequate yield under polymerization conditions which are of industrial interest.
Thus, it is known that syndiotactic polypropylene can be prepared by polymerization of propylene at −78° C. in the presence of a catalyst system consisting of VCl
4
, anisole, heptane and diisobutylaluminum chloride (compare B. Lotz et al., Macromolecules 21 (1988), 2375). However, the syndiotactic index (=76.9%) and the yield (=0.16%) are too low.
It is furthermore known that a syndiotactic polypropylene having a mow molecular weight distribution can be obtained in a significantly improved yield with the aid of a catalyst consisting of isopropylene(cyclopentadienyl)(9-fluorenyl)-zirconiun dichloride or isopropylene(cyclopentadienyl)(9-fluorenyl)-hafnium dichloride and a methylaluminoxane at a temperature of 25 to 70° C. (compare J. A. Ewen et al., J. Am. Chem. Soc., 110 (1988), 6255). Nevertheless, the molecular weight of the polymer which can be achieved with the zirconium compound is still too low and the yield which can be achieved by means of the hafnium compound is inadequate for an industrial process. Moreover, the syndiotactic characteristics which can be achieved are still in need of improvement.
There was therefore the object of discovering a process which enables syndiotactic polyolefins of high molecular weight, narrow molecular weight distribution and a syndiotactic index of more than 90% to be obtained in a high yield.
The invention thus relates to a process for the preparation of a syndiotactic polyolefin by polymerization or copolymerization of an olefin of the formula R
a
CH═CHR
b
, in which R
a
and R
b
are identical or different and denote a hydrogen atom or an alkyl radical having 1 to 28 carbon atoms, or R
a
and R
b
, with the atoms joining them, can form a ring, at a temperature of −60 to 200° C. under a pressure of 0.5 to 100 bar in solution, suspension or the gas phase in the presence of a catalyst which consists of a metallocene as the transition metal component and an aluminoxane of the formula II
for the linear type and/or of the formula III
for the cyclic type, in which, in the formulae II and III, R
9
denotes a C
1
-C
6
-alkyl group or phenyl or benzyl and n is an integer from 2 to 50, which comprises carrying out the polymerization in the presence of a catalyst, the transition metal component of which is a compound of the formula I
in which
M
1
is titanium, zirconium, vanadium, niobium or tantalum,
R
1
and R
2
are identical or different and denote a hydrogen atom, a halogen atom, a C
1
-C
10
-alkyl group, a C
1
-C
10
-alkoxy group, a C
6
-C
10
-aryl group, a C
6
-C
10
-aryloxy group, a C
2
-C
10
-alkenyl group, a C
7
-C
40
-arylalkyl group, a C
7
-C
40
-alkylaryl group or a C
8
-C
40
-arylalkenyl group,
R
3
and R
4
are different and denote a mono- or polynuclear hydrocarbon radical which can form a sandwich structure with the central atom M
1
,
R
5
is
═BR
6
, ═AlR
6
, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO
2
, ═NR
6
, ═CO, ═PR
6
or ═P(O)R
6
, in which R
6
, R
7
and R
8
are identical or different and denote a hydrogen atom, a halogen atom, a C
1
-C
10
-alkyl group, a C
1
-C
10
-fluoroalkyl group, a C
6
-C
10
-fluoroaryl group, a C
6
-C
10
-aryl group, a C
1
-C
10
-alkoxy group, a C
2
-C
10
-alkenyl group, a C
7
-C
40
-arylalkyl group, a C
6
-C
40
-arylalkenyl group or a C
7
-C
40
-alkylaryl group, or R
6
and R
7
or R
6
and R
8
, in each case with the atoms joining them, form a ring, and M
2
is silicon, germanium or tin.
The catalyst to be used in the process according to the invention consists of an aluminoxane and a metallocene of the formula I
In formula I, M
1
is a metal from the group comprising titanium, zirconium, vanadium, niobium and tantalum, preferably zirconium.
R
1
and R
2
are identical or different and denote a hydrogen atom, a C
1
-C
10
-, preferably C
1
-C
3
-alkyl group, a C
1
-C
10
-, preferably C
1
-C
3
-alkoxy group, a C
6
-C
10
-, preferably C
6
-C
8
-aryl group, a C
6
-C
10
-, preferably C
6
-C
8
-aryloxy group, a C
2
-C
10
-, preferably C
2
-C
4
-alkenyl group, a C
7
-C
40
-, preferably C
7
-C
10
-arylalkyl group, a C
7
-C
40
-, preferably C
7
-C
12
-alkylaryl group, a C
8
-C
40
-, preferably C
8
-C
12
-arylalkenyl group or a halogen atom, preferably chlorine.
R
3
and R
4
are different and denote a mono- or polynuclear hydrocarbon radical which can form a sandwich structure with the central atom M
1
.
R
3
and R
4
are preferably fluorenyl cyclopentadienyl, it also being possible for the parent structure to carry additional substituents.
R
5
is a single- or multi-membered bridge which links the radicals R
3
and R
4
and denotes
═BR
6
, ═AlR
6
, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO
2
, ═NR
6
, ═CO, ═PR
6
or P(O)R
6
, in which R
6
, R
7
and R
8
are identical or different and denote a hydrogen atom, a halogen atom, preferably chlorine, a C
1
-C
10
-, preferably C
1
-C
3
-alkyl group, in particular a methyl group, a C
1
-C
10
-fluoroalkyl group, preferably a CF
3
group, a C
6
-C
10
-fluoroaryl group, preferably a pentafluorophenyl group, a C
6
-C
10
-, preferably C
6
-C
8
-aryl group, a C
1
-C
10
-, preferably C
1
-C
4
-alkoxy group, in particular a methoxy group, a C
2
-C
10
-, preferably C
2
-C
4
-alkenyl group, a C
7
-C
40
-, preferably C
7
-C
10
-arylalkyl group, a C
8
-C
40
-, preferably C
8
-C
12
-arylalkenyl group or a C
7
-C
40
-, preferably C
7
-C
12
-alkylaryl group, or R
6
and R
7
or R
6
and R
8
, in each case together with the atoms joining them, form a ring.
M
2
is silicon, geranium or tin, preferably silicon or germanium.
R
5
is preferably ═CR
6
R
7
, ═SiR
6
R
7
, ═GeR
6
R
7
, —O—, —S—, ═SO, ═PR
6
or ═P(O)R
6
.
The metallocenes described above can be prepared in accordance with the following general reaction scheme:
Metallocenes which are preferably employed are (arylalkylidene)(9-fluorenyl)(cyclopentadienyl)zirconium dichloride, (diarylmethylene)(9-fluorenyl)(cyclopentadienyl)zirconium dichloride and (dialkylmethylene)(9-fluorenyl)(cyclopentadienyl)zirconium dichloride.
(Methyl(phenyl)methylene)(9-fluorenyl)(cyclopentadienyl-zirconium dichloride, (diphenylmethylene)(9-fluorenyl)(cyclopentadienyl)zirconium dichloride and (dimethylmethylene)(9-fluorenyl)(cyclopentadienyl)zirconium dichloride are particularly preferred here.
The cocatalyst is an aluminoxane of the formula II
for the linear type and/or of the formula III
for the cyclic type. In these formulae, the radicals R
9
denote a C
1
-C
6
-alkyl group, preferably methyl, ethyl, isobutyl, butyl or neopentyl, or phenyl or benzyl. Methyl is particularly preferred. n is an integer from 2 to 50, preferably 5 to 40. However, the exact structure of the aluminoxane is not known.
The aluminoxane can be prepared in various ways.
One possibility is careful addition of water to a dilute solution of an aluminum trialkyl by introducing in each case small portions of the solution of the aluminum trialkyl, preferably aluminum trimethyl, and the water into an initial larger amount of an inert solvent and in between each addition waiting for the evolution of gas to end.
In another process, finely powdered copper sulfate pentahydrate is suspended in toluene in a glass flask and aluminium trialkyl is added under an inert gas at about −20° C. in an amount so that about 1 mol of CuSO
4
.5H
2
O is available for every 4 Al atoms. After slow hydrolysis, alkane being split off, the reaction mixture is left at room temperature for 24 to 48 hours, during which it must be cooled if necessary, so that the temperature does not rise above 30° C. The aluminoxane dissolved in the toluene is then filtered of f from the copper sulfate and the solution is conc

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