Long carbon fibre reinforced polypropylene composition

A process for the preparation of a polypropylene composition comprising:

• a. 37.0 to 95.0 wt %, based on a total weight of the polypropylene composition, of a polypropylene base material (PBM) wherein the polypropylene base material (PBM) is:
• i. a propylene homopolymer (hPP) and/or
• ii. a propylene copolymer (cPP);
• and
• b. 4.5 to 50.0 wt %, based on the total weight of the polypropylene composition, of a carbon fiber (CF);
• and
• c. 0.5 to 13.0 wt %, based on the total weight of the polypropylene composition, of an adhesion promoter (AP),
• wherein the carbon fiber (CF) comprised in the polypropylene composition is a roving and has an average fiber length in a range of 4.0 to 17.0 mm, the polypropylene composition is present as particles with the components a) and c) forming a polymer matrix (PM) having a melt flow rate MFR2 (230° C., 2.16 kg) measured according to ISO 1133 in a range of 2.0 to 250 g/10 min and wherein an average particle length of the polypropylene composition corresponds to an average fiber length of the carbon fiber (CF), and wherein
• the propylene homopolymer (hPP) has
• a1. a melting temperature measured according to ISO 11357-3 of at least 150° C. and/or
• b1. a xylene cold soluble (XCS) content of ≤4.0 wt %, based on a total weight of the propylene homopolymer (hPP),
• the propylene copolymer (cPP) is a heterophasic propylene copolymer (HECO) having
• a2. a xylene cold soluble (XCS) content of >5.0 wt %, based on a total weight of the heterophasic propylene copolymer (HECO), and/or
• b2. a comonomer content of ≤30.0 mol %, based on a total weight of the heterophasic propylene copolymer (HECO), and
• wherein the polypropylene base material (PBM) and the adhesion promoter (AP) are the only polymeric compounds in the polypropylene composition,
• the process comprising steps of:
• a′. providing a polypropylene base material (PBM),
• b′. providing an adhesion promoter (AP),
• c′. melting the polypropylene base material (PBM) of step a) and melting the adhesion promoter (AP) of step b),
• d′. providing a carbon fiber (CF) as a continuous roving,
• e′. impregnating the carbon fiber (CF) of step d′) with a first part of the polypropylene base material (PBM1) and with a whole of the adhesion promoter (AP) of step c′) and subsequently coating a thus impregnated carbon fiber (CF) with a remaining second part of the polypropylene base material (PBM2) to obtain a carbon fiber (CF) reinforced polypropylene material, and
• f′. solidifying and cutting the carbon fiber (CF) reinforced polypropylene material into particles with an average particle length in a range of 4.0 to 17.0 mm to obtain the polypropylene composition.