Propylene random copolymer and process for the production thereof

摘要

The present invention relates to a process for preparing a propylene random copolymer comprising polymerisation of propylene with a comonomer, said comonomer being ethylene or an alpha -olefin comprising at least four carbon atoms, in the presence of a catalyst in a multistage process comprising polymerisation of propylene with a comonomer in a first reaction zone including at least one slurry reactor to give a first polymerisation product, transferring said first product to a second reaction zone including at least one gas phase reactor and polymerisation of propylene with a comonomer in said gas phase reactor in the presence of said first polymerisation product, wherein the temperature in the gas phase reactor is higher than that in the slurry reactor and to a polymer obtainable by this process. Furthermore, the invention relates to a propylene random copolymer prepared by copolymerisation of propylene with a comonomer wherein the distribution of the comonomer determined according to the TREF method is multimodal, preferably bimodal, a propylene random copolymer prepared by copolymerisation of propylene with a comonomer wherein the copolymer is having an elution interval determined according to the TREF method of 50 DEG C or more, a propylene random copolymer prepared by copolymerisation of propylene with a comonomer, wherein the random copolymer is a unimodal polymer and the elution interval determined by the TREF method is given by the equation Y≤4.5 . m + 16 wherein Y is the elution interval in DEG C and m is the percentage of ethylene in the copolymer in wt.%, and to the use of such a copolymers for the production of a film, of an article by blow moulding or injection moulding, of a fibre or of a pipe.