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 polymerization catalyst comprising a solid catalyst component is subjected to a prepolymerization reaction in a prepolymerization 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 copolymerized in the presence of the prepolymerized 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 prepolymerized catalyst in such a process.