Process for preparing heterophasic propylene copolymers

A process for the preparation of a heterophasic propylene copolymer, the process comprising:

• preparing the heterophasic propylene copolymer in the presence of a single site catalyst comprising:
• (i) a complex of formula (I):
• wherein
• M is zirconium or hafnium;
• each X independently is a sigma-donor ligand
• L is a divalent bridge selected from —R′2C—, —R′2C—CR′2—, —R′2Si—, —R′2Si—SiR′2—, or —R′2Ge—, wherein each R′ is independently a hydrogen atom or a C1-C20-hydrocarbyl group optionally containing one or more heteroatoms of Group 14-16 of the periodic table or fluorine atoms, or optionally two R′ groups taken together can form a ring;
• R1 and R1′ are each independently hydrogen, C5-C10-aryl or a group —CH(Rx)2 wherein each Rx is independently H or a C1-10 hydrocarbyl group, and optionally the two Rx taken together can form a ring,
• R2 and R2′ are each independently hydrogen, C5-C10-aryl or a group —C(Ry)3 wherein each Ry is independently H or a C1-10 hydrocarbyl group, or optionally two or three Ry groups taken together can form a ring,
• whereby at least one of R1 or R2 and one of R1′ or R2′ is different from hydrogen, and
• whereby R2 together with one of R1, as well as R2′ together with one of R1′ may be part of a further mono- or multicyclic ring condensed to the phenyl ring,
• R3 and R3′ are each independently a linear C1 to C6 hydrocarbyl group or a branched or cyclic C4 to C10 hydrocarbyl group, whereby the groups are not branched in α-position,
• R4 and R4′ are each independently a tertiary C4 to C10 hydrocarbyl group,
• R5 and R5′ are each independently a linear or branched C1 to C10 alkyl group or an C5-C10-aryl group, and
• (ii) a cocatalyst comprising a compound of a group 13 metal,
• the heterophasic propylene copolymer comprising:
• (a-1) a matrix (M) that is a polypropylene homopolymer or propylene-ethylene random copolymer, and
• (a-2) an elastomeric propylene-ethylene copolymer (E) dispersed in said matrix (M),
• wherein the elastomeric propylene-ethylene copolymer (E) has:
• (i) an intrinsic viscosity (IV) determined according to DIN ISO 1628/1 (in decalin at 135° C. in a range of from 3.1 to 8.0 dl/g,
• (ii) an ethylene comonomer content in a range of from 10.0 to 80.0 wt %,
• (iii) optionally a second comonomer selected from 1-butene in an amount of from 0.0 to up to 20.0 wt % or 1-hexene in an amount of from 0.0 up to 10.0 wt %, and
• (iv) a xylene soluble (XS) fraction (determined according to ISO 16152 at 25° C.) of at least 50.0 wt %, and
• wherein a xylene soluble fraction (determined according to ISO 16152 at 25° C.) of the heterophasic propylene copolymer is in a range of from 5.0 to 50.0 wt %.