Polyolefin composition for medium/high/extra high voltage cables with improved electrical breakdown strength

1. A cable comprising a layer made of a polyolefin composition comprising:

(i) a polyolefin (A); and

(ii) an aromatic compound (B) which is an anthracene derivative having the following structural unit according to the following Formula (I.A):

wherein, in Formula (I.A):

R1, R2, R3, R4, R5, R6, R7, R8, R11, and R13 are independently hydrogen or a hydrocarbyl group optionally containing heteroatoms selected from the group consisting of Si, N, P, O and S;

or at least two adjacent substituents selected from the group consisting of R1, R2, R3, R4, R5, R6, R7, R8, R11, and R13, together with the carbon atoms of the ring system of formula (I.A) to which the substituents are attached, form a further aromatic or non-aromatic ring fused to the ring system of formula (I.A), and wherein the further aromatic or non-aromatic ring is optionally substituted with 1 to 8 substituents R1′ to R8′, independently selected from hydrogen or a hydrocarbyl group optionally containing heteroatoms selected from the group consisting of Si, N, P, O and S;

or one or more carbons which form the aromatic ring of Formula (IA) is heteroatom, N, and the corresponding R group is absent;

with the provisos that:

(a) at least one of said R1, R2, R3, R4, R5, R6, R7, R8, R11 or R13 or, if present, R1′ to R8′ is selected from the groups of —O(R9) and —NR(R10)2, wherein R9 and R10 are alkyl groups with at least 6 C-atoms which may or may not contain a functional group at the end which, if present, is a —CH═CH2, a halogen, a hydroxyl, a carboxylic acid or acid halide group; and

(b) if any of R1, R2, R3, R4, R5, R6, R7, R8, R11 or R13 or, if present, any of R1′ to R8′ is a hydrocarbyl group optionally containing heteroatoms selected from the group consisting of Si, N, P, O and S, and is attached to an aromatic ring of the compound according to Formula (I.A), said hydrocarbyl group lacks H-atoms in the alpha-position.

2. The cable of claim 1 , wherein the aromatic compound (B) is 9,10-dioctyloxyanthracene.

3. The cable of claim 1 , wherein the polyolefin (A) comprises a polyethylene or polypropylene.

4. The cable of claim 1 , wherein the polyolefin (A) comprises a polyethylene which has been produced by a high pressure process using free radical polymerization resulting in low density polyethylene (LDPE).

5. The cable of claim 1 , wherein the layer made of the polyolefin composition is an insulation layer.

6. A medium, high or extra high voltage cable comprising one or more conductors in a cable core, an inner semiconductive layer, followed by an insulation layer and then an outer semiconductive layer, wherein at least one of these layers comprises a polyolefin composition comprising:

(i) a polyolefin (A); and

(ii) an aromatic compound (B) which is an anthracene derivative having the following structural unit according to the following Formula (I.A):

wherein, in Formula (I.A):

R1, R2, R3, R4, R5, R6, R7, R8, R11, and R13 are independently hydrogen or a hydrocarbyl group optionally containing heteroatoms selected from the group consisting of Si, N, P, O and S;

or at least two adjacent substituents selected from the group consisting of R1, R2, R3, R4, R5, R6, R7, R8, R11, and R13, together with the carbon atoms of the ring system of formula (I.A) to which the substituents are attached, form a further aromatic or non-aromatic ring fused to the ring system of formula (I.A), and wherein the further aromatic or non-aromatic ring is optionally substituted with 1 to 8 substituents R1′ to R8′, independently selected from hydrogen or a hydrocarbyl group optionally containing heteroatoms selected from the group consisting of Si, N, P, O and S;

or one or more carbons which form the aromatic ring of Formula heteroatom, N, and the corresponding R group is absent;

with the provisos that:

(a) at least one of said R1, R2, R3, R4, R5, R6, R7, R8, R11 or R13 or, if present, R1′ to R8′ is selected from the groups of —O(R9) and —NR(R10)2, wherein R9 and R10 are alkyl groups with at least 6 C-atoms which may or may not contain a functional group at the end which, if present, is a —CH═CH2, a halogen, a hydroxyl, a carboxylic acid or acid halide group; and

(b) if any of R1, R2, R3, R4, R5, R6, R7, R8, R11 or R13 or, if present, any of R1′ to R8′ is a hydrocarbyl group optionally containing heteroatoms selected from the group consisting of Si, N, P, O and S, and is attached to an aromatic ring of the compound according to Formula (I.A), said hydrocarbyl group lacks H-atoms in the alpha-position.

7. The cable of claim 6 , wherein the aromatic compound (B) is 9,10-dioctyloxyanthracene.

8. The cable of claim 6 , wherein the polyolefin (A) comprises a polyethylene or polypropylene.

9. The cable of claim 6 , wherein the polyolefin (A) comprises a polyethylene which has been produced by a high pressure process using free radical polymerization resulting in low density polyethylene (LDPE).

10. The cable of claim 6 , wherein the insulation layer comprises the polyolefin composition.