Process for cross-linking thermoplastic polyolefin elastomer compositions

Abstract

A process for cross-linking an elastomer-containing thermoplastic polyolefin composition comprising the steps of preparing a masterbatch by mixing and/or masticating an elastomeric polyolefin with a cross-linking co-agent, and optionally an additive, in the presence of a thermoplastic polyolefin; then, cooling the masterbatch obtained in the preceding step at least up to the solidification of the thermoplastic polyolefin; and finally mixing and/or masticating the masterbatch, after the cooling step, with a cross-linking agent and optionally an additive.

1 . A process for cross-linking an elastomer-containing thermoplastic polyolefin composition comprising the steps of:
 1) preparing a masterbatch by mixing and/or masticating an elastomeric polyolefin with a cross-linking co-agent, and optionally an additive, in the presence of a thermoplastic polyolefin;   2) cooling the masterbatch obtained in step (1) at least up to the solidification of the thermoplastic polyolefin; and   3) mixing and/or masticating the masterbatch, after the cooling step 2, with a cross-linking agent and optionally an additive,
 wherein the elastomer-containing thermoplastic polyolefin composition is obtained in a polymerization process carried out in two or more sequential process stages, and comprises: 
   A) from 10 to 60 parts of a homopolymer of propylene or a random copolymer of propylene with ethylene and/or a C 4 -C 8  α-olefin, containing more than 80% of propylene, said homopolymer or copolymer being insoluble in xylene at ambient temperature for more than 80%;   B) from 0 to 25 parts of an essentially linear semicrystalline copolymer of ethylene containing propylene and/or a C 4 -C 8  α-olefin, insoluble in xylene at ambient temperature; and   C) from 15 to 87 parts of a copolymer of ethylene with propylene and/or a C 4 -C 8  α-olefin, or mixture thereof, said copolymer containing from 25 to 75% of ethylene and being soluble in xylene at ambient temperature.   
   
   
       2 - 6 . (canceled)