Process for the manufacture of branched polypropylene

Process for the manufacture of a branched polypropylene having a branching index g 'of less than 1.00, wherein the process comprises the step polymerizing propylene and optionally another (s) comonomer (s) under non-supercritical conditions in a reaction vessel, characterized in that a. The pressure during the polymerization of propylene and optionally another (s) comonomer (s) in said reaction vessel is at least 45,4 bar, b. The temperature during the polymerization of propylene and optionally another (s) comonomer (s) in said reaction vessel is below 90 and c. The polymerization of propylene and optionally another (s) comonomer (s) is conducted in said reaction vessel in the presence of a catalyst system having a not greater surface area of ​​350 m 2 / g measured according to ISO 9277 and said catalyst system comprises a metallocene catalyst having zirconium as the transition metal and wherein the metallocene catalyst has the formula (I): wherein z is 0 or 1, (Cp) 2R zZrX 2 X is independently a monovalent anionic ligand, R is a bridging group linking the two Cp ligands, and the two Cp-ligands are selected independently of one another from the group consisting of cyclopentadienyl ring unsubstituted indenyl ring, unsubstituted ring tetrahydroindenyl, unsubstituted fluorenyl ring unsubstituted , substituted cyclopentadienyl ring, substituted indenyl ring, substituted tetrahydroindenyl ring, and substituted fluorenyl ring, and said Cp-ligands differ in their chemical structure.