High speed cross-linking of grafted plastomers

A process for providing a cross-linked composition, the process comprising the steps of

• (a) providing an ethylene-α-olefin plastomer which is a copolymer of ethylene and 1-octene and providing no other polymer, the ethylene-α-olefin plastomer having
• a density of from 850 kg/m3 to 900 kg/m3;
• and
• a melt flow rate (ISO 1133, 2.16 kg, 190° C.) of 0.3 to 50 g/10 min;
• (b) grafting the ethylene-α-olefin plastomer from step (a) with a silane crosslinker such that the content of the silane crosslinker is in the range of 0.1 to 10.0 wt. % with respect to the resulting grafted ethylene-α-olefin plastomer;
• and
• (c) contacting said grafted ethylene-α-olefin plastomer from step (b) with 2 to 8 wt. % of a tin-free silane crosslinking catalyst with respect to the resulting mixture of grafted ethylene-α-olefin plastomer and tin-free silane crosslinking catalyst to form an intermediate composition, which in turn forms a cross-linked composition having a gel content of at least 60% when subjected to 23° C. and 50% humidity for 15 minutes, and wherein said tin-free catalyst comprises a sulfonic acid;
• wherein step c) is carried out:
• in an extruder;
• and/or
• at a temperature 120 to 210° C.