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
1998-09-11
2002-04-02
Wood, Elizabeth D. (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...
C502S102000, C502S103000
Reexamination Certificate
active
06365537
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a two-component supported catalyst, its preparation and its use for the polymerisation of unsaturated compounds, especially of conjugated dienes, in the gas phase.
2. Description of the Prior Art
The polymerisation of conjugated dienes in solution has the disadvantage that, when the unreacted monomer and the solvent are separated from the polymer that has formed, low-molecular weight compounds can enter the environment via outlet air and waste water and therefore have to be disposed of by appropriate means. In addition, large quantities of solvents have to be used and separated off with high energy costs. The solvents are generally flammable and easy to ignite and therefore represent a potential hazard.
In recent years, the gas-phase process has proved particularly advantageous for the preparation of polyethylene and polypropylene in particular, and has become established in the industry. The advantages of the gas-phase process are primarily based on the fact that no solvents are used and emissions and waste water contaminations can be reduced.
Supported catalysts have been developed for implementing the gas-phase process, Ziegler-Natta catalysts being used among others. The supported catalysts may be prepared by impregnating the supporting material with solutions of the metal compounds and with solutions of the co-catalysts, simultaneously or consecutively, so that all of the catalyst is applied on to one supporting material. Examples of this include catalysts based on the rare earths (e.g. DE 43 34 045, EP 727 447, WO 96/31543, WO 96/31544). During this supporting process, the Ziegler-Natta catalyst is bonded to the supporting material in a catalytically active form and is thus very sensitive to impurities. Another disadvantage lies in the fact that the catalyst can age when stored for a prolonged period, which is accompanied by a change in catalyticselectivity and activity. This has a disadvantageous effect on product qualities and space time yields.
Another variant for preparing catalysts for gas-phase polymerisation consists in that, during polymerisation, one or more catalyst components in dissolved form are sprayed into the reaction chamber in which there is e.g. a fluidised bed of inert solid particles (cf. e.g. WO 96/04323, WO 96/0432, U.S. Pat. No. 5,453,471).
It is a disadvantage of these catalysts that part of the catalyst system is sprayed into the gas-phase process in solution, as a result of which solvent can accumulate in the reactor, especially in a continuous process. The solvent then has to be removed from the polymerisation product again, which makes the gas-phase process less economical. Furthermore, the polymer may stick together as a result of swelling with the solvent, especially in the case of dienes, and therefore a large quantity of powdered material is required in the reaction bed. Since this can lead to a reduction in product quality, large quantities of powdered material should be avoided if possible.
Another method of preparing catalysts is known for the gas-phase polymerisation of polyolefins. According to DE 26 23 693, the transition metal compound is used in solid form, an organometallic compound is applied on to a suitable supporting material and the gas-phase polymerisation of ethylene is carried out with a mixture of the two catalyst components.
In WO 96/10542, catalysts are described in which the transition metal compound and the organometallic compound are bonded on to supporting materials separately and the mixture of the two components is used for the polymerisation of olefins. In the patent examples, the same supporting material (Davison 948 silica) is used for both catalyst components and the polymerisation takes place after superposition of the two components. The supporting material “Davison 948 silica” consists of spherical agglomerates with an average particle diameter of 30 to 100 &mgr;m and is often used for gas-phase polymerisations.
The catalysts described in WO 96/10542 for the preparation of polyolefins are used with methylaluminoxane as co-catalyst. Based on the metallocene compounds used as the transition metal compound (TM compounds), the co-catalyst is used in a high molar excess, a further excess of co-catalyst having no disadvantageous effect on the activity of the catalyst, so that the maximum proportion of the co-catalyst in the catalyst system is primarily limited by economic considerations.
When preparing catalysts for the gas-phase polymerisation of conjugated dienes, on the other hand, it must be ensured that the molar ratio of TM compound to special components of the co-catalysts is kept within narrow limits, too much or too little of this component leading to the deactivation of the catalyst system.
Because the polymers tend to stick together, the catalyst has to be kept moving during the polymerisation, e.g. by stirring or by a gas stream, in order to prevent the catalyst particles from sticking together during the polymerisation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The object of the present invention is now to avoid the disadvantages of the supported catalysts used up to the present for the polymerisation of diolefins in the gas phase and to provide supported catalysts which may be used without solvents, are particularly stable in storage and simple to produce, and match or even exceed the supported catalysts known up to the present in terms of activity, selectivity and reaction conditions, and may be used in the production of polymers having a tendency to stick together.
SUMMARY OF THE INVENTION
The present invention therefore provides a two-component supported catalyst consisting of
a) at least one transition metal compound applied on to an inorganic or polymeric organic supporting material, the transition metal being selected from the group of the d and f elements of the periodic table according to Mendeleev
b) at least one organometallic compound applied on to an inorganic or polymeric organic supporting material, the metal being selected from the group of the IIa, IIb and IIIb elements of the periodic table [(F. A. Cotton, G. Wilkinson,
Anorganische Chemie, 4th edition, VCH Verlagsgesellschaft mbH, Weinheim, 1985)] and
c) optionally at least one modifier which is supported on a) and/or on b),
the transition metal compound in component a) being used in quantities of 0.1 to 100 mmol, based on 100 g of the supporting material, and the organometallic compound in component b) being used in quantities of 0.1 to 1000 mmol, based on 100 g of the supporting material, and component c) being used in quantities of 0 to 500 mmol, based on 100 g of the supporting material, and the supporting materials of components a) to b) being used in quantitative ratios by weight (g/g) of 1:10
−3
to 1000, and at least one of components a) or b) having a supporting material with an average particle size before and/or during polymerisation of <25 &mgr;m, preferably <10 &mgr;m, particularly preferably <2 &mgr;m.
The transition metal compound in component a) is preferably used in quantities of 0.5 to 50 mmol, based on 100 g of the supporting material, and the organometallic compound in component b) is preferably used in quantities of 0.5 to 500 mmol, based on 100 g of the supporting material, and the modifier in component c) is preferably used in quantities of 0 to 250 mmol, based on 100 g of the supporting material.
The molar ratio of the compounds of components a) to b) to c) applied on to the supporting materials depends on the catalyst system used. Those molar ratios known for the Ziegler-Natta catalyst systems in solution polymerisation are preferably used. The molar ratios of components a):b):c) are 1:1 to 10 000:0 to 1000, preferably 1:1 to 1000:0 to 100.
Those transition metal compounds used for Ziegler-Natta catalysts for diene polymerisation are preferably used for component a). The rare earth elements, such as lanthanum, cerium, praseodyrnium, neodymium, terbium, dysprosium, holmium, erbium, as well as titanium, zi
Steinhauser Norbert
Windisch Heike
Bayer AG
Wood Elizabeth D.
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