Modified heterophasic polyolefin composition

A method of making a heterophasic polyolefin polymer composition comprising the steps of:

• (a) providing a propylene polymer phase comprising propylene polymers selected from the group consisting of polypropylene homopolymers and copolymers of propylene and up to 50 weight % of ethylene and/or C4-C10 α-olefins, and an ethylene polymer phase comprising ethylene polymers selected from the group consisting of ethylene homopolymers and copolymers of ethylene and C3-C10 α-olefins provided that the ethylene content of the ethylene polymer phase is at least 8 weight %,
• (b) providing a masterbatch composition comprising a compatibilizing agent and a chemical free radical generator in a carrier resin, wherein the compatibilizing agent is selected from the group consisting of compounds that have (i) at least one nitroxide radical or are capable of producing at least one nitroxide radical while being melt compounded with the polyolefin polymer composition;
• and (ii) at least one unsaturated bond capable of undergoing a radical addition reaction, wherein the compatibilizing agent is present in the masterbatch composition in an amount of about 1 wt. % to about 80 wt. % based on the total weight of the masterbatch composition;
• and
• (c) mixing the propylene polymer phase, the ethylene polymer phase and the masterbatch composition to produce free carbon radicals, whereby the compatibilizing agent reacts with propylene polymers and ethylene polymers thereby bonding propylene polymers to ethylene polymers, and whereby the propylene polymer phase and the ethylene polymer phase form a heterophasic composition.