Highly filled soft polyolefin composition for roofing membrane

A filled polyolefin composition having a MFR (230° C./2.16 kg) of from 2 to 7/10 min comprising:

• a) 35 to 65% by weight of a flexible heterophasic polyolefin composition (I), comprising the following fractions:
• A) from greater than 40 to 55% by weight of a crystalline polymer fraction consisting of a copolymer of propylene with ethylene;
• the copolymer containing at least 85% by weight of units derived from propylene, and the crystalline fraction having a fraction insoluble in xylene at 25° C. of at least 90% by weight;
• B) from 45 to less than 60% by weight of an elastomeric fraction consisting of a copolymer or blend of copolymers of ethylene with propylene;
• the copolymer or blend containing units derived from ethylene in a quantity lower than 40% by weight;
• and
• the fraction soluble in xylene at 25° C. of the polyolefin composition (I) having an IVgpc lower than 2.5 dl/g, a broad molecular weight distribution Mw/Mn (GPC) equal to or higher than 4, and a Mz/Mw (GPC) equal to or higher than 2.5;
• b) 30 to 80% by weight of an inorganic filler (II) selected from flame-retardant inorganic fillers and inorganic oxides or salts;
• and
• c) 2 to 25% by weight of a butene-1 copolymer having a flexural modulus (ISO 178) lower than 60 MPa, a Shore A (ISO 868) lower than 90 and a Tg (DMTA) lower than −20° C.;
• wherein the sum of a), b) and c) is 100%.