Process for treatment of an initial polypropylene-containing material to produce a polypropylene composition for injection molding

A process for treatment of an initial polypropylene-containing material to produce a polypropylene composition characterized in that it comprises the following steps:

• a) providing a twin screw extruder with thermal regulation devices;
• b) providing an initial polypropylene-containing material comprising at least 50 wt. % of polypropylene based on the total weight of the initial polypropylene-containing material;
• c) extruding the initial polypropylene-containing material to obtain a polypropylene composition;
• and
• d) recovering a polypropylene composition;
• wherein step (c) of extruding comprises a thermal treatment of the initial polypropylene-containing material at a maximum barrel temperature Ts of at least 345° C. in one or more hot zones of the extruder;
• and wherein the maximum barrel temperature Ts is obtained by self-heating of the material wherein the one or more hot zones have a total length equal to or greater than 6 D with D being the screw diameter, wherein the extrusion is performed with mechanical specific energy greater than or equal to 0.30 kWh/kg, wherein the screw profile comprises at least one hot zone with successive kneading blocks elements over a length of at least 4 D followed by a left-handed element with D being the screw diameter, wherein the thermal regulation devices, are set to initial imposed barrel temperatures ranging between 24° and 320° C. and are switched off when the barrel temperature in the zone spontaneously exceeds the imposed barrel temperature by at least 3° C. without the need of external heat application.