Process for the production of propylene copolymers using a prepolymerised catalyst

The present invention relates to a process for the production of propylene copolymers wherein - in a first step an olefin polymerisation catalyst comprising a solid catalyst component is subjected to a prepolymerisation reaction in a prepolymerisation reactor, in which propylene monomers are present in an amount of 98.0 to 99.9 mol% and further alpha-olefin monomers other than propylene are present in an amount of 0.1 to 2.0 mol%, based on the combined amount of propylene and further alpha-olefin monomers, so that a prepolymer is produced on the catalyst in an amount of 10 to 1000 g per g of the solid catalyst component, and - in a second, subsequent step propylene and further alpha-olefin monomers other than propylene are copolymerised in the presence of the prepolymerised catalyst produced in the first step so that a propylene copolymer is obtained which contains at least 0.1 mol% of alpha-olefin units other than propylene, to propylene copolymers obtainable by such a process and to the use of a prepolymerised catalyst in such a process.