Optimum external co-catalyst electron donor molar ratio in propylene polymerization
AssigneeFina Technology, Inc.
InventorsEdwar Shoukri Shamshoum, David John Rauscher
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Abstract
This invention is for a process for the polymerization of propylene to a minimum level of xylene solubles by use of the molar ratio of co-catalyst to external electron donor (selectivity control agent). Using a conventional supported heterogeneous Ziegler-Natta catalyst component with an trialkyl aluminum co-catalyst and an cycloalkylalkyldialkoxysilane external electron nor (selectivity control agent) in a Al/Si molar ratio of about results in the minimum amount of xylene solubles.
Claims4
A catalyst for the polymerization of propylene monomer to a polypropylene product wherein the xylene solubles are minimized, said catalyst comprising:
- a) a conventional supported Ziegler-Natta transition metal compound catalyst component for the polymerization of propylene having the general formula MR+x where M is a Group IVB metal, R+ is selected from the group consisting of a halogen and a hydrocarbyloxy, R+ being the same or different with at least one R+ being a halogen, and x is the valence of the metal;
- b) an aluminum trialkyl co-catalyst described by the formula AlR′3 where R′ is an alkyl of from 1-8 carbon atoms and R′ may be the same or different;
- and
- c) cyclohexylmethyldimethoxylsilane as an external electron donor;
- wherein the molar ratio of co-catalyst to external electron donor is 2.
A process for making a catalyst for the polymerization of propylene monomer to a polypropylene product wherein the xylene solubles are minimized by the steps comprising:
- a) selecting a conventional supported Ziegler-Natta transition metal compound catalyst component having the general formula MR+x where M is a Group IVB metal, R+ is selected from the group consisting of a halogen and a hydrocarbyloxy, R+ being the same or different with at least one R+ being a halogen, and x is the valence of the metal for the polymerization of propylene;
- b) contacting that catalyst component with an aluminum trialkyl co-catalyst described by the formula AlR′3 where R′ is an alkyl of from 1-8 carbon atoms and R′ may be the same or different;
- and
- c) contacting said catalyst component with cyclohexylmethyldimethoxysilane as an external electron donor either simultaneously with or after step b),
- wherein the molar ratio of co-catalyst to external electron donor is 2.
Dependencies are inferred from the claim text.