Polyolefin composition for medium/high/extra high voltage cables comprising benzil-type voltage stabiliser

1. A polyolefin composition comprising

a. a polyolefin (A),

b. a benzil derivative voltage stabilizer (B) comprising the structural unit according to the following formula (I):

wherein

R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 independently are hydrogen, or a hydrocarbyl group which optionally contain heteroatoms selected from the group consisting of Si, N, Po, O, and S;

or at least two of said R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 together with the ring atoms of the ring system of formula (I) they are attached to, form a further aromatic or non-aromatic ring fused to the ring system of formula (I), and wherein the ring system of formula (I) with said at least one fused further ring optionally further bear one to eight substituents, R1′ to R8′, each of which are independently selected from said same groups as R1 to R10; and

n=2 to 9;

with the proviso that

(i) at least one of said R1, R2, R3, R4, R5, R6, R7, R8, R9 or R10, or at least one of said R1′ to R8′, is selected from the group consisting of —N(R11)(R12) —Ar—N(R11)(R12), —O(R13), and —Ar—O(R13), wherein R11 and R12 are independently hydrocarbyl groups which optionally contain heteroatoms, Ar is an aryl group which optionally contain heteroatoms, and R13 is H or a hydrocarbyl group which optionally contain heteroatoms.

2. The polyolefin composition according to claim 1 wherein said n is 2 to 6.

3. The polyolefin composition according to claim 1 , wherein said hydrocarbyl group of proviso (i) contains a heteroatom selected from the group consisting of Si, N, P, O and S.

4. The polyolefin composition according to claim 1 wherein said heteroatom is N and said hydrocarbyl group of proviso (i) contains a tert.-amine group.

5. The polyolefin composition according to claim 1 wherein R11 and R12, independently are an aryl or alkyl group.

6. The polyolefin composition according to claim 1 wherein R13 is an aryl or alkyl group.

7. The polyolefin composition according to claim 1 wherein N(R11)(R12) is in para-position to the carbonyl function in the compound of formula (I).

8. The polyolefin composition according to claim 1 wherein O(R13) is in para-position to the carbonyl function in the compound of formula (I).

9. The polyolefin composition according to claim 7 , wherein both R8 and R3 are substituted with said —N(R11)(R12).

10. The polyolefin composition according to claim 8 , wherein both R8 and R3 are substituted with said —O(R13).

11. The polyolefin composition according to claim 1 wherein R11 and R12 independently are an alkyl group, which optionally contain a functional group at the end opposite to the respective ring atom.

12. The polyolefin composition according to claim 1 wherein R13 is an alkyl group, which optionally contains a functional group at the end opposite to the respective ring atom.

13. The polyolefin composition according to claim 1 wherein R11 and R12 independently contain from 1 to 50 carbon atoms.

14. The polyolefin composition according to claim 1 wherein R13 contains from 1 to 50 carbon atoms.

15. The polyolefin composition according to claim 1 wherein R11 and R12 independently contain from 6 to 18 carbon atoms.

16. The polyolefin composition according to claim 1 wherein R13 contains from 6 to 18 carbon atoms.

17. The polyolefin composition according to claim 1 wherein R11 and R12 independently contain from 6 to 12 carbon atoms.

18. The polyolefin composition according to claim 1 wherein R13 contains from 6 to 12 carbon atoms.

19. A cable comprising a layer made of the polyolefin composition according to claim 1 .

20. A method for the production of a layer of a cable wherein the polyolefin composition according to claim 1 is used.

21. A method for the production of a layer of a cable wherein a polyolefin composition according to claim 1 is used.

22. A method for the production a polyolefin composition utilizing a benzil derivative (B) as a voltage stabiliser, the benzil derivative (B) comprising the structural unit according to the following formula (I):

wherein

R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 independently are hydrogen, or a hydrocarbyl group which optionally contain heteroatoms selected from the group consisting of Si, N, Po, O, and S;

or at least two of said R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 together with the ring atoms of the ring system of formula (I) they are attached to, form a further aromatic or non-aromatic ring fused to the ring system of formula (I), and wherein the ring system of formula (I) with said at least one fused further ring optionally further bear one to eight substituents, R1′ to R8′, each of which are independently selected from said same groups as R1 to R10; and

n is 2 to 9;

with the proviso that

(i) at least one of said R1, R2, R3, R4, R5, R6, R7, R8, R9 or R10, or at least one of said R1′ to R8′, is selected from the group consisting of —N(R11)(R12) —Ar—N(R11)(R12), —O(R13), and —Ar—O(R13), wherein R11 and R12 are independently hydrocarbyl groups which optionally contains heteroatoms, Ar is an aryl group which optionally contains heteroatoms, and R13 is H or a hydrocarbyl group which optionally contain heteroatoms.

23. The polyolefin composition according to claim 1 , wherein the benzil derivative voltage stabilizer (B) consists of the structural unit according to formula (I).

24. The method according to claim 22 , wherein the benzil derivative voltage stabilizer (B) consists of the structural unit according to formula (I).

25. The polyolefin composition according to claim 1 , wherein the heteroatom is N.

26. The method according to claim 22 , wherein the heteroatom is N.