High performance Ziegler-Natta catalyst systems, process for producing such MgCl₂based catalysts and use thereof

摘要

Improved Ziegler-Natta catalysts and methods of making the improved catalyst are described. The Ziegler-Natta catalyst is formed using a spherical MgCl2-xROH support, where R is a linear, cyclic or branched hydrocarbon unit with 1-10 carbon atoms and where ROH is an alcohol or a mixture of at least two different alcohols and where x has a range of about 1.5 to 6.0, preferably about 2.5 to 4, more preferably about 2.9 to 3.4, and even more preferably 2.95 to 3.35. The Ziegler-Natta catalyst includes a Group 4-8 transition metal and an internal donor comprising a diether compound. The catalyst has improved activity in olefin polymerization reactions as well as good stereoregularity and hydrogen sensitivity, and may be useful in the production of phthalate-free propylene polymers having a molecular weight distribution (PI(GPC)) in the range from about 5.75 to about 9.

主权项

1. A process for producing a Ziegler-Natta catalyst for the polymerization of olefins comprising the steps of:
a. combining a spherical spray-cooled MgCl2-xROH support, wherein x is in the range of from about 1.5 to about 6.0 and ROH is an alcohol or a mixture of alcohols where R is a linear, cyclic, or branched hydrocarbon unit with 1-10 carbon atoms, with a transition metal compound in a reactor at a temperature of between about −30° C. and +40° C.; b. heating the mixture in the reactor to a temperature of between about 30° C. to about 100° C.; c. concurrent with the heating in step (b), or following reaching the temperature of step (b), adding an internal electron donor consisting essentially of a diether compound to the mixture in the reactor, wherein the diether is selected such that the resulting catalyst has an activity and hydrogen response resulting in the production of propylene polymers having a molecular weight distribution in the range from about 5.75 to about 9; d. heating the resulting mixture to at least about 80′C, and holding the resulting mixture at that temperature for about 1 to 3 hours to produce a pre-catalyst; e. filtering the mixture containing the pre-catalyst while still hot to obtain the solid pre-catalyst component; f. extracting the pre-catalyst with a mixture of an organic solvent and a transition metal compound at a temperature of at least 100° C. for 1-5 hours to form a catalyst; and g. washing the catalyst with a hydrocarbon solvent and drying the catalyst under vacuum and/or elevated temperature of 30-100° C.