Copolymer composition for semiconductive cable layer

1. A composition for a semiconductive layer of a cable, comprising

(a) a heterophasic copolymer of propylene,

(b) a polar copolymer comprising ethylene and at least one polar comonomer bearing a polar group, the polar comonomer being selected from C 1 - to C 6 -alkyl acrylates, C 1 - to C 6 -alkyl methacrylates, acrylic acids, methacrylic acids and vinyl acetate, wherein the polar copolymer has a density of from 900 kg/m 3 to 945 kg/m 3 ,

(c) a solid conductive filler, and

(d) a polyolefin functionalised with a mono- or polycarboxylic acid compound or a derivative of a mono- or polycarboxylic acid compound, wherein said functionalised polyolefin has a melt flow rate (230° C., 2.16 kg) of from 0.5 to 500 g/10 min and further wherein said mono- or polycarboxylic acid compound or a derivative of a mono- or polycarboxylic acid compound is not the polar comonomer present in the polar copolymer (b);

and wherein the composition has a Charpy Notch Impact Strength of at least 10 kJ/m 2 at −20° C., measured in accordance with ISO 179-1eA:2000,

wherein said composition is not crosslinked by the addition of a crosslinking agent.

2. A composition according to claim 1 wherein the solid conductive filler is a carbon black.

3. A composition according to claim 1 wherein the heterophasic copolymer of propylene comprises a polypropylene homopolymer or random copolymer matrix and dispersed therein a second propylene copolymer.

4. A composition according to claim 3 wherein the second propylene copolymer dispersed in the matrix has a weight average particle size of less than 1 μm.

5. A composition according to claim 1 wherein the composition has a melt flow rate (230° C., 5.0 kg) from 0.01 to 30.0 g/10 min.

6. A composition according to claim 1 , wherein the polar groups of the polar copolymer (b) are incorporated by copolymerising an ethylene monomer with at least one polar comonomer or by grafting a polar group bearing compound to a polymer.

7. A composition according to claim 1 wherein the polar copolymer (b) is characterized by a melt flow rate (190° C., 2.16 kg) of from 0.05 to 20.0 g/10 min.

8. A composition according to claim 1 , wherein the heterophasic copolymer of propylene has a melt flow rate (230° C., 2.16 kg) of from 0.05 to 20.0 g/10 min.

9. A composition according to claim 1 wherein the mono- or polycarboxylic acid compound or a derivative of a mono- or polycarboxylic acid compound of the functionalised polyolefin (d) is a linear or cyclic anhydride of a mono- or polycarboxylic acid.

10. A composition according to claim 1 , wherein the composition has a Charpy Notch Impact Strength of at least 15 kJ/m 2 at −20° C. when measured in accordance with ISO 179-1eA:2000.

11. A composition according to claim 1 , wherein the composition comprises the heterophasic copolymer of propylene of from 40 to 99.5 wt % based on the combined weight (100 wt %) of the heterophasic copolymer of propylene, the polar copolymer (b) and the functionalised polyolefin (d) present in the composition.

12. A composition according to claim 1 , wherein the composition comprises the polar copolymer (b) in an amount of from 1.0 to 65 wt % based on the combined weight (100 wt %) of the heterophasic copolymer of propylene, the polar copolymer (b) and the functionalised polyolefin (d) present in the composition.

13. A composition according to claim 1 , wherein the composition comprises the solid conductive filler (c) in an amount of up to 50 wt % based on the total amount (100 wt %) of the composition.

14. A composition according to claim 1 , wherein the composition comprises the functionalised polyolefin (d) in an amount of up to 10.0 wt % based on the total amount (100 wt %) of the composition.

15. A composition according to claim 1 , wherein the polar copolymer is ethylene methyl acrylate (EMA), ethylene ethyl acrylate (EEA), ethylene butyl acrylate (EBA) or ethylene vinyl acetate.

16. A composition according to claim 1 , wherein polyolefin (d) is maleic anhydride (MAH) grafted polypropylene.

17. A composition for a semi conductive layer of a cable, comprising

(a) a heterophasic copolymer consisting of a propylene homopolymer or random propylene ethylene copolymer matrix and a propylene copolymer with ethylene, wherein the heterophasic copolymer has a melt flow rate (230° C., 2.16 kg) of from 0.05 to 20.0 g/10 min,

(b) a polar copolymer comprising ethylene and at least one polar comonomer bearing a polar group, the polar comonomer being selected from C 1 - to C 6 -alkyl acrylates, C 1 - to C 6 -alkyl methacrylates, acrylic acids, methacrylic acids and vinyl acetate, wherein the polar copolymer has a density of from 900 kg/m 3 to 945 kg/m 3 ,

(c) a solid conductive filler and, optionally,

(d) a polyolefin functionalised with a mono- or polycarboxylic acid compound or a derivative of a mono- or polycarboxylic acid compound, wherein said mono- or polycarboxylic acid compound or a derivative of a mono- or polycarboxylic acid compound is other than the polar comonomer(s) present in the polar copolymer (b);

and wherein the composition has a Charpy Notch Impact Strength of at least 10 kJ/m 2 at −20° C., measured in accordance with ISO 179-1eA:2000.

18. A cable comprising the composition according to claim 1 , wherein (1) the cable comprises a conductor surrounded by at least a semiconductive layer comprising the composition of claim 1 or (2) the cable comprises a conductor surrounded by in the following order at least an inner semiconductive layer, an insulation layer and an outer semiconductive layer, wherein at least the inner semiconductive layer, the outer semiconductive layer, or both comprises the composition of claim 1 .

19. A composition according to claim 1 , wherein the polar copolymer is produced by high pressure polymerization of ethylene and at least one polar comonomer.

20. A composition according to claim 19 , wherein the high pressure polymerization is conducted at a pressure of from 70 MPa to 400 MPa and a temperature of from 80° C. to 400° C.