Cable with recyclable covering

1. A cable comprising at least one electrical conductor and at least one extruded covering layer based on a thermoplastic polymer material in admixture with a dielectric liquid, wherein:

said thermoplastic material comprises a propylene homopolymer or a copolymer of propylene with at least an olefin comonomer selected from ethylene and an α-olefin other than propylene, said homopolymer or copolymer having a melting point greater than or equal to 140° C. and a melting enthalpy of from 30 to 100 J/g; and

said liquid comprises at least one alkylaryl hydrocarbon with at least two non-condensed aromatic rings and a ratio of number of aryl carbon atoms to total number of carbon atoms greater than or equal to 0.6.

2. A cable as claimed in claim 1 , wherein the ratio of number of aryl carbon atoms to total number of carbon atoms is greater than or equal to 0.7.

3. A cable as claimed in claim 1 , wherein the propylene homopolymer or copolymer has a melting point of from 145 to 170° C.

4. A cable as claimed in claim 1 , wherein the propylene homopolymer or copolymer has a melting enthalpy of from 30 to 85 J/g.

5. A cable as claimed in claim 1 , wherein the propylene homopolymer or copolymer has a flexural modulus, measured at ambient temperature, of from 30 to 1400 MPa.

6. A cable as claimed in claim 1 , wherein the propylene homopolymer or copolymer has a flexural modulus, measured at ambient temperature, of from 60 to 1000 MPa.

7. A cable as claimed in claim 1 , wherein the propylene homopolymer or copolymer has a melt flow index, measured at 230° C., of from 0.5 to 10.0 dg/min.

8. A cable as claimed in claim 1 , wherein the propylene homopolymer or copolymer has a melt flow index, measured at 230° C., of from 0.5 to 5.0 dg/min.

9. A cable as claimed in claim 1 , wherein the olefin comonomer is present in a quantity of less than or equal to 15 mol %.

10. A cable as claimed in claim 1 , wherein the olefin comonomer is present in a quantity of less than or equal to 10 mol %.

11. A cable as claimed in claim 1 , wherein the olefin comonomer is ethylene or an α-olefin of formula CH 2 ═CH—R, wherein R is a linear or branched C 2 -C 10 alkyl.

12. A cable as claimed in claim 11 , wherein the α-olefin is selected from 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene or combinations thereof.

13. A cable as claimed in claim 2 , wherein the thermoplastic material is selected from:

a) a propylene homopolymer or a copolymer of propylene with at least one olefin comonomer selected from ethylene and an α-olefin other than propylene, having a flexural modulus of from 30 to 900 MPa; and

b) a heterophase copolymer comprising a thermoplastic phase based on propylene and an elastomeric phase based on ethylene copolymerized with an α-olefin, in which the elastomeric phase is present in a quantity of at least 45 wt % based on the total weight of the heterophase copolymer.

14. A cable as claimed in claim 13 , wherein the propylene homopolymer or copolymer under a) has a flexural modulus of from 50 to 400 MPa.

15. A cable as claimed in claim 13 , wherein the propylene homopolymer or copolymer under a) has:

a melting point of from 140 to 165° C.;

a melting enthalpy of from 30 to 80 J/g;

a fraction soluble in boiling diethyl ether in an amount of less than or equal to 12 wt %, having a melting enthalpy of less than or equal to 4 J/g;

fraction soluble in boiling n-heptane in an amount of from 15 to 60 wt %, having a melting enthalpy from 10 to 40 J/g; and

a fraction insoluble in boiling n-heptane in an amount of from 40 to 85 wt %, having a melting enthalpy of greater than or equal to 45 J/g.

16. A cable as claimed in claim 13 , wherein the propylene homopolymer or copolymer of a) has:

a fraction solution in boiling diethyl ether in an amount of from 1 to 10 wt %, having a melting enthalpy of less than or equal to 2 J/g;

a fraction soluble in boiling n-heptane in an amount of from 20 to 50 wt %, having a melting enthalpy of from 15 to 30 J/g; and

a fraction insoluble in boiling n-heptane in an amount of from 50 to 80 wt %, having a melting enthalpy from 50 to 95 J/g.

17. A cable as claimed in claim 13 , wherein the α-olefin included in the elastomeric phase of the heterophase copolymer under b) is propylene.

18. A cable as claimed in claim 17 , wherein the elastomeric phase consists of an elastomeric copolymer of ethylene and propylene comprising from 15 to 50 wt % of ethylene and from 50 to 85 wt % of propylene based on the weight of the elastomeric phase.

19. A cable as claimed in claim 1 , wherein a base thermoplastic material is the propylene homopolymer or copolymer of propylene in mechanical mixture with a low crystallinity polymer having a melting enthalpy of less than or equal to 30 J/g, and a quantity of less than or equal to 70 wt % based on the total weight of the thermoplastic material.

20. A cable as claimed in claim 19 , wherein the low crystallinity polymer is in a quantity of from 20 to 60 wt % based on the total weight of the thermoplastic material.

21. A cable as claimed in claim 19 , wherein the low crystallinity polymer is a copolymer of ethylene with a C 3 -C 12 α-olefin.

22. A cable as claimed in claim 19 , wherein the low crystallinity polymer is a copolymer of ethylene with an α-olefin and a diene.

23. A cable as claimed in claim 21 or 22 , wherein the ethylene copolymer is selected from

i) a copolymer having the following monomer composition: 35-90 mol % of ethylene; 10-65 mol % of α-olefin; and 0-10 mol % of a diene; or

ii) a copolymer having the following monomer composition: 75-97 mol % of ethylene; 3-25 mol % of α-olefin; and 0-5 mol % of a diene.

24. A cable as claimed in claim 23 , wherein the ethylene copolymer is selected from a copolymer having the following monomer composition: 90-85 mol % of ethylene; 5-10 mol % of α-olefin; and 0-2 mol % of a diene.

25. A cable as claimed in claim 21 , wherein the α-olefin is selected from propylene, 1-hexene and 1-octene.

26. A cable as claimed in claim 22 , wherein the diene has from 4 to 20 carbon atoms.

27. A cable as claimed in claim 22 , wherein the diene is selected from a conjugated or non-conjugated linear diolefin, and a monocyclic or polycyclic diene.

28. A cable as claimed in claim 22 , wherein the diene is selected from 1,3-butadiene, 1,4-hexadiene, 1,6-octadiene, 1,4-cyclohexadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-vinyl-2-norbornene, or their mixtures.

29. A cable as claimed in claim 1 , wherein the alkylaryl hydrocarbon has a dielectric constant at 25° C. of less than or equal to 3.5.

30. A cable as claimed in claim 1 , wherein the dielectric constant at 25° C. is less than or equal to 3.

31. A cable as claimed in claim 1 , wherein the dielectric liquid has a kinematic viscosity at 20° C. of between 1 and 500 mm 2 /s.

32. A cable as claimed in claim 1 , wherein the dielectric liquid has a kinematic viscosity at 20° C. of between 5 and 100 mm 2 /s.

33. A cable as claimed in claim 1 , wherein the alkylaryl hydrocarbon has a hydrogen absorption capacity of greater than or equal to 5 mm 3 /min.

34. A cable as claimed in claim 33 , wherein the hydrogen absorption capacity is greater than or equal to 50 mm 3 /min.

35. A cable as claimed in claim 1 , further comprising an epoxy resin added to the dielectric liquid in a quantity of less than or equal to 1 wt % based on the weight of the liquid.

36. A cable as claimed 35 , wherein the alkylaryl hydrocarbon is present in a quantity of greater than or equal to 10 wt % based on the total weight of the dielectric liquid.

37. A cable as claimed in claim 1 , wherein the dielectric liquid comprises at least one alkylaryl hydrocarbon having at least three non-condensed aromatic rings.

38. A cable as claimed in claim 1 , wherein the alkylaryl hydrocarbon has the structural formula:

where:

R 1 , R 2 , R 3 and R 4 , equal or different, are hydrogen or methyl;

n1 and n2, equal or different, are zero, 1 or 2, with the proviso that the sum n1+n2 is less than or equal to 3.

39. A cable as claimed in claim 1 , wherein the alkylaryl hydrocarbon is selected from benzyltoluene, benzylxylene, (methylbenzyl)toluene, (methylbenzyl)xylene, dibenzyltoluene, dibenzylxylene, di(methylbenzyl)toluene, di(methylbenzyl)xylene, or their mixtures.

40. A cable as claimed in claim 1 , wherein the dielectric liquid comprises at least one triphenylmethane, either unsubstituted or substituted by at least one radical selected from methyl, benzyl and methylbenzyl.

41. A cable a claimed in claim 40 , wherein the triphenylmethane is selected from ditoluylphenylmethane, dixylylphenylmethane, xylyltoluylphenylmethane, or their mixtures.

42. A cable as claimed in claim 1 , wherein the weight ratio of dielectric liquid to base polymer material is 1:99 to 25:75.

43. A cable as claimed in claim 1 , wherein the weight ratio of dielectric liquid to base polymer material is from 2.98 to 20:80.

44. A cable as claimed in claim 1 , wherein the weight ratio of dielectric liquid to base polymer material is from 3:97 to 15:85.

45. A cable as claimed in claim 1 , wherein the extruded covering layer is a layer with electrical insulation properties.

46. A cable as claimed in claim 1 , wherein the extruded covering layer is a layer with semiconductive properties.

47. A cable as claimed in claim 46 , wherein the conductive filler is dispersed in the layer with semiconductive properties.

48. A cable as claimed in claim 1 , wherein the base polymer material is selected from propylene homopolymers or copolymers comprising at least 40 wt % of amorphous phase, based on the total polymer weight.

49. A cable as claimed in claim 1 , wherein at least one layer with electrical insulation properties and at least one layer with semiconductive properties are present.

50. A copolymer composition comprising a thermoplastic polymer material which comprises a propylene homopolymer or a copolymer of propylene with at least an olefin comonomer selected from ethylene and an α-olefin other than propylene, said homopolymer or copolymer having a melting point greater than or equal to 140° C. and a melting enthalpy of from 30 to 100 J/g, in admixture with a dielectric liquid which comprises at least one alkylaryl hydrocarbon with at least two non-condensed aromatic rings and a ratio of number of aryl carbon atoms to total number of carbon atoms of greater than or equal to 0.6.

51. A cable as claimed in claim 22 , wherein the α-olefin is selected from propylene, 1-hexene and 1-octene.