Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
1999-04-21
2001-04-17
Wu, David W. (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S108000, C502S104000, C502S116000, C502S152000, C502S235000, C502S238000, C526S160000, C526S943000
Reexamination Certificate
active
06218330
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a new process for preparing supported metallocene-alumoxane catalysts and their use in the polymerization or copolymerization of olefins.
DESCRIPTION OF THE PRIOR ART
Olefin (co)polymerization catalysts comprising a metallocene and an alumoxane have been known for a long time. European patent application no. 0 035 242 discloses a process for preparing ethylene and atactic propylene polymers in the presence of a halogen free cyclopentadienyl transition metal salt and an alumoxane.
The use of the homogeneous metallocene-alumoxane catalyst systems in the continuous olefin polymerization processes leads to several drawbacks. Indeed it invariably causes severe reactor wall fouling and crust formation, and further the resulting polymers are very fluffy and exhibit very low bulk densities.
In order to solve these problems, it was proposed to work with heterogeneous metallocene-alumoxane catalyst systems. For example these supported metallocene-alumoxane catalysts are described in European patent no. 0 619 325.
Known methods for preparing supported metallocene-alumoxane catalysts are disclosed in Makromol. Chem., Rapid Commun. 14, 239-243, 1993 (W. Kaminsky).
None of the above-mentioned patents and article reports about successful use (high activity, absence of reactor fouling) of any supported metallocene-alumoxane catalyst for the polymerization or copolymerization of olefins.
U.S. Pat. No. 5,240,894 relates to a process for producing a supported metallocene-alumoxane catalyst comprising forming an alumoxane-metallocene reaction solution, adding a porous support, evaporating the resulting slurry so as to remove residual solvent from the support and optionally prepolymerizing the catalyst with olefinic monomer. According to the description it is mentioned that the temperature maintained during reaction of the metallocene/alumoxane solution and support can be vary such as, for example, from 0° C. to 100° C. However all the examples given mention reaction mixtures heated at temperatures not higher than 66° C. Experiments were carried out by the Applicant and showed that when the contact between the metallocene/alumoxane and the support is made at the temperatures exemplified the efficiency catalyst of the so obtained supported catalytic system in the polymerization or copolymerization of olefins is not sufficiently high for an industrial application and yet an important reactor fouling is formed.
SUMMARY OF THE INVENTION
One of the aims of the present invention is consequently to overcome the above-mentioned drawbacks and to provide a process for preparing a supported metallocene-alumoxane catalyst having a surprisingly high activity and low reactor fouling.
To this end, according to the present invention, said process which comprises the following steps:
a) reacting a metallocene with an alumoxane at a temperature comprised between 15 and 50° C.,
b) recovering from step a) a mixture comprising an alkylmetallocenium cation and an anionic alumoxane oligomer,
c) reacting said mixture with a support, and
d) recovering a supported metallocene-alumoxane catalyst as a dry solid,
is characterized in that the reaction of step c) is carried out at a temperature comprised between 85° C. and 110° C., preferably at a temperature comprised between 90 and 110° C., and most preferably at 110° C.
According to an advantageous embodiment of the invention, the duration of the reaction of step c) is between 60 and 120 minutes, preferably of about 90 minutes.
The invention also relates to a process for the polymerization or copolymerization of olefins comprising contacting at least one olefinic monomer in the presence of a supported catalyst thus obtained.
REFERENCES:
patent: 4933403 (1990-06-01), Kaminsky et al.
patent: 5057475 (1991-10-01), Canich et al.
Debras Guy
Razavi Abbas
Choi Ling-Siu
Fina Research, S. A.
Wheelington Jim D.
Wu David W.
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