Process for enhancing the melt strength of propylene-based polymer compositions

Process for preparation of a propylene-based polymer composition comprising the steps of:

• (a) mixing a propylene-based polymer and a peroxydicarbonate in a mixing device, wherein the mixing takes place at a temperature of ≤30° C., wherein the peroxydicarbonate is introduced into the mixing process in a dry form, thereby obtaining a mixed composition;
• (b) keeping the mixed composition at a temperature of ≤30° C.;
• (c) feeding the mixed composition into a melt extruder via a feed inlet located in a first section of the melt extruder;
• (d) homogenizing the mixed composition fed into the first section of the melt extruder that is maintained at a temperature of ≤75° C. where the propylene-based polymer is in solid state in the first section of the melt extruder during an average residence time of ≥6.0 and ≤30.0 seconds;
• (e) further homogenizing the mixed composition fed into the melt extruder in a subsequent second section of the melt extruder at a temperature at which the propylene-based polymer is in the molten state, thereby obtaining a homogenized material;
• and
• (f) extruding the homogenized material from a die outlet of the melt extruder followed by cooling and solidification;
• wherein the steps (a) through (f) are conducted in that order.