Polymerization catalyst systems, their production and use

Details Polymerization catalyst systems, their production and use Polymerization catalyst systems, their production and use

1997-03-13

2003-08-12

Bell, Mark L. (Department: 1755)

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

Catalyst or precursor therefor

Plural component system comprising a - group i to iv metal...

C502S107000

Reexamination Certificate

active

06605560

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to catalysts, catalyst systems and to methods for their production and use in olefin polymerization. The invention particularly relates to process for preparing a supported metallocene catalyst system.
BACKGROUND OF THE INVENTION
It is well known in the art that metallocene catalysts and catalyst systems are quite soluble in many liquids, particularly those diluents or reactive components used in a typical olefin polymerization processes. In addition, metallocene catalysts can also be affected chemically and physically by various components typically used in a commercial polymerization process. Metallocene catalyst components and catalyst system components have a tendency toward fouling and/or sheeting in a gas phase and slurry polymerization processes. In a continuous gas phase process, in particular, fouling on the walls of the reactor/can result in many problems including poor heat transfer in the polymerization process. Polymer particles that adhere to the walls of the reactor continue to polymerize and often fuse together and form chunks, which can be detrimental to a continuous process, particularly a fluidized bed process. In a continuous slurry process fouling on the walls of the reactor, which act as the heat transfer surface, can result in many problems including poor heat transfer. In addition these catalysts often provide polymer products that are low in bulk density and therefore are difficult to handle and transfer.
As a result of the reactor operability issues associated with using metallocene catalysts and catalyst systems various techniques for supporting or producing a metallocene catalyst system with reduced tendencies for fouling have been developed. For example, U.S. Pat. No. 5,283,278 is directed towards the prepolymerization of a support metallocene catalyst. U.S. Pat. No. 5,332,706 describes a method for forming a support metallocene catalyst using an incipient impregnation technique where a very small volume of solution is mixed with a silica support. While these possible solution might reduce fouling or sheeting somewhat, it is expensive to employ and may not reduce both fouling and sheeting to a level sufficient for the successful operation of a continuous process, particularly a commercial or large-scale process.
Thus, it would be highly advantageous to have an improved polymerization catalyst that in a polymerization process would significantly enhance reactor operability.
SUMMARY OF THE INVENTION
This invention is generally directed towards a new polymerization catalyst system, to methods for its manufacture and to its use in a polymerization process.
In one embodiment a method is provided to produce a supported catalyst system by contacting a carrier, a metallocene catalyst component and an activator in a vacuum. The supported catalyst is then brought to ambient pressure for use as a polymerization catalyst.
In an alternative embodiment, a method for producing a supported catalyst system is provided where the supported catalyst system is produced in a vessel having a starting pressure, the pressure is then increased above the starting pressure during or after contacting a carrier with a liquid. The liquid may comprise a metallocene catalyst component or an activator or both.
In another embodiment of the invention, there is provided a process for producing polyolefins by contacting olefin monomer, optionally with at least one comonomer in the presence of the catalyst system described above.
In yet another embodiment there is provided a catalyst system produced by the improved method.
DETAILED DESCRIPTION OF THE INVENTION
Introduction
This invention is generally directed toward the formation of a supported catalyst system useful for polymerizing olefins. It is known in the art that catalyst can be vacuum dried after formation. This invention relates to the formation of a supported catalyst system under a vacuum. The invention also relates to the formation of a supported catalyst system where during application of the catalyst bearing solvent to the carrier or after the formation of supported catalyst system, the supported catalyst system is subjected to an environment creating a pressure differential from the outside to the inside of the particles of the supported catalyst system. The method for forming the catalyst system of the invention results in a polymerization catalyst with reduced fouling tendencies resulting in improved reactor operability.
Making the catalyst of the invention as described above results in a simple, commercially useful and cost effective supported catalyst system with a reduced tendency for sheeting or fouling in a polymerization reactor without a reduction in catalytic activity.
Catalyst Components and Catalyst Systems of the Invention
Metallocene catalysts, for example, are typically those bulky ligand transition metal compounds derivable from the formula:
[
L]
m
M[A]
n
where L is a bulky ligand; A is leaving group or a univalent anionic ligand, M is a transition metal and m and n are such that the total ligand valency corresponds to the transition metal valency. Preferably the catalyst is four co-ordinate such that the compound is ionizable to a 1
+
charge state.
If two ligands L are present they may be bridged. The metallocene compound may be full-sandwich compounds having two or more ligands L, which may be cyclopentadienyl ligands or cyclopentadiene derived ligands, or half-sandwich compounds having one ligand L, which is a cyclopentadienyl ligand or derived ligand.
In one embodiment, at least one ligand L has a multiplicity of bonded atoms, preferably 4 to 30 carbon atoms, that typically is a cyclic structure or ring system such as a ligand, which may be substituted or unsubstituted. Non-limiting examples of ligands include a cyclopentadienyl ligand, or a cyclopentadienyl derived ligand such as an indenyl ligand, a benzindenyl ligand or a fluorenyl ligand and the like or any other ligand capable of &eegr;-5 bonding to a transition metal atom. One or more of these bulky ligands may be &pgr;-bonded to the transition metal atom. The transition metal atom may be a Group 4, 5 or 6 transition metal and/or a metal from the lanthanide and actinide series, U.S. Pat. No. 5,350,723 incorporated herein by reference, preferably the transition metal is of Group 4. Other ligands may be bonded to the transition metal, such as a leaving group, such as but not limited to hydrocarbyl, hydrogen, silyl or any other univalent anionic ligand. Non-limiting examples of metallocene catalysts and catalyst systems are discussed in for example, U.S. Pat. Nos. 4,530,914, 4,871,705, 4,937,299, 5,124,418, 5,017,714, 5,120,867, 5,278,264, 5,278,119, 5,304,614, 5,324,800 all of which are herein fully incorporated by reference. Also, the disclosures of EP-A-0 591 756, EP-A-0 520 732, EP-A-0 420 436, WO 91/04257 WO 92/00333, WO 93/08221, and WO 93/08199 are all fully incorporated herein by reference.
Further, the metallocene catalyst component of the invention can be a monocyclopentadienyl heteroatom containing compound. This heteroatom is activated by either an alumoxane, an ionizing activator, a Lewis acid or a combination thereof to form an active polymerization catalyst system. These types of catalyst systems are described in, for example, PCT International Publication WO 92/00333, WO 94/07928, and WO 91/04257, WO 94/03506, U.S. Pat. Nos. 5,057,475, 5,096,867, 5,055,438, 5,198,401, 5,227,440 and 5,264,405 and EP-A-0 420 436, all of which are fully incorporated herein by reference. In addition, the metallocene catalysts useful in this invention can include non-cyclopentadienyl catalyst components, or ancillary ligands such as boroles or carbollides in combination with a transition metal or can be a bimetallic transition metal compound. Additionally it is within the scope of this invention that the metallocene catalysts and catalyst systems may be those described in U.S. Pat. Nos. 5,064,802, 5,145,819, 5,149,819, 5,243,001, 5,239,022, 5,276,208, 5,296,434, 5,321,106, 5,329,031,

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