Process for the preparation of 1-olefin polymers

Details Process for the preparation of 1-olefin polymers Process for the preparation of 1-olefin polymers

1999-12-14

2001-01-09

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...

C526S160000, C526S166000, C526S943000, C502S103000, C502S117000

Reexamination Certificate

active

06172168

ABSTRACT:

The invention relates to a process for the preparation of 1-olefin polymers having a high degree of isotacticity and an advantageous particle size distribution.
In recent times supported catalysts in which transition metal compounds have been applied, together with suitable electron donors, to supports, for example magnesium chloride, have been used for the preparation of polyolefins having a high degree of isotacticity. Aluminum alkyls are used as activators in the polymerization reaction and donors, such as ethyl benzoate or Ph
2
Si(OR)
2
, are used as stereo regulators to poison non-stereospecific centers.
Since these catalysts consist mainly of MgCl
2
, relatively high chlorine contents of 30-300 pps are found in the polymers prepared with them, unless these residues are removed by a special after-treatment.
Soluble Ziegler catalysts based on a bis-(cyclopentadienyl)-zirconium alkyl or halide in combination with oligomeric aluminoxanes area also known. These catalysts make it possible to polymerize ethylene and propylene with a moderate activity, but no isotactic polypropylene is obtained.
It is also known of the catalyst system bis-(cyclopentadienyl)-titaniumdiphenyl/methyl aluminoxane that it is capable of converting polypropylene into stereo block polymers, i.e. polypropylene having relatively long isotactic sequences (cf. U.S. Pat. No. 4,522,982). Important disadvantages of this catalyst system are the unsuitability for large scale industry of the polymerization temperatures (0° to −60° C.) and the unsatisfactory activity of the catalyst.
Finally, it is possible to prepare isotactic polypropylene in a suspension polymerization by means of a stereo-rigid and chiral zirconium compound, together with an aluminoxane (cf. EP-A 185,918=U.S. Ser. No. 801,683). The polymer has a narrow molecular weight distribution, which is advantageous for certain fields of use, for example for high-speed injection molding. At the same time the catalyst system has a number of drawbacks. Owing to the low activity, an involved purification of the polymer is required to remove the large residual amounts of catalyst. The bulk density of the polymer is too low and the particle morphology and the particle size distribution are unsatisfactory. In addition, the polymerization is carried out in toluene which has to be purified and freed from moisture and oxygen in a very expensive manner.
It was required to find a catalyst which does not have the disadvantages of the known catalyst.
It has been found that a preactivation of the metallocene by means of an aluminoxane effects a considerable increase in the activity of the catalyst system and an improvement in the particle morphology of the polymer.
The invention therefore relates to a process for the preparations of a 1-olefin polymer by polymerizing a 1-olefin of the formula R—CH═CH
2
in which R is an alkyl group having 1 to 28 carbon atoms or copolymerizing these olefins together with ethylene at a temperature from −60 to 200° C., under a pressure of 0.5 to 60 bar, in solution, in suspension or in the gas phase and in the presence of a catalyst which is composed of a metallocene as the transition metal compound and an aluminoxane as the activator, which comprises carrying out the polymerization in the presence of a catalyst in which the transition metal component has been preactivated for 5 minutes to 60 hours, at a temperature from −78 to 100° C., by means of an aluminoxane of the formula IV
for the linear type and/or of the formula V
for the cyclic type, R
17
in the formulae IV and V being a C
1
-C
6
-alkyl group and p being an integer from 2 to 50, and the activator also being an aluminoxane of the formulae IV and/or V.
A variety of metallocene catalysts can be employed for the process according to the invention.
Stereo-rigid, chiral metallocenes are used for the preparation of highly isotactic poly-1-olefins. These metallocenes have the formula I
In this formula
Me
1
is a metal of group IV b or V b of the periodic system of the elements, i.e.. titanium, zirconium, hafnium, vanadium, niobium, or tantalum, preferably titanium or zirconium and particularly zirconium.
R
1
and R
2
are identical or different and denote a C
1
-C
10
-alkyl group, preferably a C
1
-C
3
-alkyl group, a C
6
-C
10
-aryl group, preferably a C
6
-C
8
-aryl group, a C
2
-C
10
-alkenyl group, preferably a C
2
-C
4
-alkenyl group, a C
7
-C
40
-aralkyl group, preferably a C
7
-C
10
-aralkyl group, a C
8
-C
40
-arylalkenyl group, preferably a C
8
-C
12
-arylalkenyl group or a halogen atom, preferably chlorine.
R
3
is a linear C
1
-C
4
, preferably C
1
-C
3
, hydrocarbon radical or a cyclic C
4
-C
6
hydrocarbon radical; these hydrocarbon radicals can contain at least one heteroatom as a bridge unit in the chain. The bridge R
3
can also be composed only of heteroatoms.
Examples of single-membered bridge units are —CR
2
6
—, —O—, —S—, —SO—, —Se—, —SeO—, —NR
6
—, —PR
6
—, AsR
6
—, —BR
6
—, —ALR
6
—, —SiR
2
6
— and —GeR
2
6
—, R
6
being a hydrogen atom, a C
6
-C
10
-aryl group, preferably a C
6
-C
8
-aryl group, a C
1
-C
10
-alkyl group, preferably a C
1
-C
4
-alkyl group, a C
2
-C
10
-alkenyl group, preferably a C
2
-C
6
-alkenyl group, a C
7
-C
40
-aralkyl group, preferably a C
7
-C
10
-aralkyl group, a C
8
-C
40
-arylalkenyl group, preferably a C
8
-C
12
-arylalkenyl group or a halogen atom, preferably chlorine. The bridge units containing —CR
2
6
— and silicon and sulfur are preferred.
Examples of two-membered bridge units are —(CR
2
6
)
2
—, —SS—, —SeSe—, —SiR
2
6
SiR
2
6
—, —SiR
2
6
CR
2
6
—.
Examples of multi-membered bridge units are —(CR
2
6
)
3
—, —(CR
2
6
)
4
—, —SiR
2
6
OSiR
2
6
—, —SiR
2
6
(CR
2
6
)
n
SiR
2
6
—, —SiR
2
6
(CR
2
6
)
n
—, —S(CR
2
6
)
n
S—, —S(CR
2
6
)
n
—, —NR
6
(CR
2
6
)
n
NR—, —NR
6
(CR
2
6
)
n
—, —PR
6
(CR
2
6
)
n
PR
6
—, —PR
6
(CR
2
6
)
n
— in which n=1 or 2 or —ALR
6
DAlR
6
—, R
6
having the meaning mentioned above. Bridge units containing —(CR
2
6
)
2
—, —(CR
2
6
)
3
— and silicon and sulfur are preferred.
R
4
and R
5
are identical or difference, preferably identical. They are mononuclear or multinuclear hydrocarbon radicals which, together with the central atom, can form a sandwich structure. Examples of radicals of this type are the indenyl, tetrahydroindenyl or cyclopentadienyl group and heteroaromatic ligands. Metallocenes which are particularly preferred are bisindenylzirconius dichlorides.
The optically active metallocenes are employed in the form of a racemate. The pure D-form or L-form can, however, also be used. An optically active polymer can be prepared by means of these pure stereoisomeric forms. However, the meso-form of the metallocenes must be removed, since the active center for polymerization (the metal atom) in these compounds is no longer chiral owing to mirror symmetry at the central metal.
The separation of the stereoisomers is known in principle (H. H. Brintzinger et al. Journal of Organometallic Chemistry, 232 (1982) 233 and 328 (1987)87).
The stereo-rigid, chiral metallocenes described above can be prepared by the following scheme of reactions:
A metallocene of the formula II
is employed for the polymerization, according to the invention, of 1-olefins to give stereo-block polymers. In this formula Me
1
has the abovementioned meaning.
R
7
and R
8
are identical or different and denote a halogen atom, C
1
-C
10
-alkyl, C
6
-C
10
-aryl, C
2
-C
10
-alkenyl, C
7
-C
40
-arylalkyl, C
7
-C
40
-alkylaryl or C
8
-C
40
-alkenylaryl.
R
9
and R
10
are identical or different and denote a substituted cyclopentadienyl radical, this radical containing one or more centers of chirality and having been formed by the reaction of an alkali metal cyclopentadienide with a sulfonic acid ester of a chiral alcohol.
In formula II Me
1
is preferably zirconium and R
7
and R
8
preferably denote a halogen atom or an alkyl group, preferably methyl and particularly a chlorine atom. R
9
and R
10
are formed by the reaction of an alkali metal cyclopentadienide, preferably sodium cyclopentadienide, and a

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