Electric cable and a method for the production thereof

An electrical cable comprising a conductor which, in the order from inside outward, is surrounded by an inner semiconducting layer, an insulating layer, and an outer semiconducting layer,

• wherein said inner semiconducting layer and/or said outer semiconducting layer when the outer semiconducting layer is non-strippable is derived from a semiconducting composition which, based on the total weight of the composition, comprises
• (a) 50-90% by weight of an ethylene copolymer;
• (b) carbon black in an amount at least sufficient to make the composition semiconducting;
• (c) 0-8% by weight of a peroxide cross-linking agent;
• and
• (d) 0-8% by weight of conventional additives,
• wherein the ethylene copolymer (a) is a heterogeneous ethylene-alkyl(meth)acrylate copolymer with the comonomer units distributed non-randomly in the polymer chains, which besides ethylene moieties comprises 2-10 mole % of an alkyl(meth)acrylate comonomer moiety, chosen from the group consisting of:
• methyl(meth)acrylate, ethyl(meth)acrylate, (iso)propyl(meth)acrylate and butyl(meth)acrylate, and the melting point of which is at least 95° C. and is higher than (108.5-1.7×(mole % of alkyl(meth)acrylate comonomer)) degree centigrade.

A method of producing a cross-linked, semiconducting layer of an electric cable including a conductor which, in the order from inside and outwards, is surrounded by an inner semiconducting layer, an insulating layer, and an outer semiconducting layer, at least one of said inner and outer semiconducting layers being derived from a cross-linkable, semiconducting composition which, based on the total weight of the composition, comprises

• (a) 50-90% by weight of an ethylene copolymer,
• (b) carbon black in an amount at least sufficient to make the composition semiconducting,
• (c) 0.2-8% by weight of a peroxide cross-linking agent,
• (d) 0-8% by weight of conventional additives,
• characterised in that
• the ethylene copolymer (a) is a heterogeneous ethylene-alkyl(meth)acrylate copolymer, which besides ethylene moieties comprises 2-10 mole % of an alkyl(meth)acrylate comonomer moiety, chosen among methyl(meth)acrylate, ethyl(meth)acrylate, (iso-)propyl(meth)acrylate and butyl(meth)acrylate, and the melting point of which is at least 95° C. and is higher than (108.5−1.7×(mole % of alkyl(meth)acrylate comonomer)) degree centigrade, and that the composition is cross-linked at a temperature of 300-400° C.