| abstract |
The invention relates to a process for producing a polypropylene composition using a first extruder comprising successive zones comprising a first zone, a second zone, a third zone and a fourth zone and a second extruder comprising successive zones comprising a first zone and a second zone, the process comprising the steps of: 1a) introducing a first propylene-based polymer in the first zone of the first extruder, 1b) melt mixing the first propylene-based polymer in the second zone of the first extruder, 1c) adding an additive masterbatch to the mixture of step 1b) in the third zone of the first extruder and 1d) melt-mixing the mixture of step 1c) in the fourth zone of the first extruder to obtain the polypropylene composition, wherein the maximum temperature in the fourth zone of the first extruder is lower than the maximum temperature in the second zone of the first extruder and is lower than 240 ºC, wherein the additive masterbatch is produced in the second extruder by a process comprising the steps of: 2a) introducing a second propylene-based polymer and organic additives in the first zone of the second extruder and 2b) melt mixing the mixture of step 2a) in the second zone of the second extruder to obtain the additive masterbatch, wherein the maximum temperature in the second zone of the second extruder is lower than the maximum temperature in the second zone of the first extruder and is lower than 240 ºC. |