Electrical oil formulation

1. An electrical oil formulation consisting essentially of:

(i) at least 80 wt % of a base oil component comprising a paraffinic base oil having a paraffin content of greater than 80 wt % paraffins and a saturates content of greater than 98 wt % and comprising a series of iso-paraffins having n, n+1, n+2, n+3 and n+4 carbon atoms and wherein n is between 20 and 35;

(ii) an phenolic or amine anti-oxidant additive;

(iii) an aromatic anti-gassing compound;

(iv) a copper passivator additive; and

(v) a sulphur or phosphorus containing additive;

wherein the base oil component has a flash point of at least 170° C., as determined by ISO 2592;

wherein the paraffinic base oil is obtained by hydroisomerisation of a Fischer-Tropsch derived wax, followed by dewaxing; and

wherein the formulation comprises between 0.05 and 10 wt % of an aromatic anti-gassing compound selected from the group consisting of:

tertrahydronaphthalene, diethylbenzene, di-isopropylbenzene, mixtures of alkylbenzenes, and mixtures of 2,6-di-t-butyl phenol and 2,6-di-t-butyl cresol.

2. The formulation according to claim 1 , wherein the paraffin base oil has a kinematic viscosity at 40° C. of between 1 and 200 mm 2 /sec.

3. The formulation according to claim 1 , wherein the paraffin base oil has a kinematic viscosity at 40° C. of between 1 and 15 mm 2 /sec, a pour point of below −30° C.

4. The formulation according to claim 1 , wherein the content of the anti-oxidant additive is between 0.04 and 0.4 wt %.

5. The formulation according to claim 1 , wherein the copper passivator is a compound according to formula (II) or a substituted or unsubstituted benzotriazole compound represented by the formula (III)

wherein R4 may be hydrogen or a group represented by the formula (IV)

or by the formula (V)

wherein:

c is 0, 1, 2 or 3;

R 3 is a straight or branched C 1-4 alkyl group; R 5 is a methylene or ethylene group; R 6 and R 7 are hydrogen or the same or different straight or branched alkyl groups of 1-18carbon atoms; R 8 and R 9 are the same or different alkyl groups of 3-15 carbon atoms.

6. The formulation according to claim 5 , wherein R 3 is methyl or ethyl and c is 1 or 2.

7. The formulation according to claim 1 , wherein between 10 mg/kg and 0.3 wt % of a di-t-butylated hydroxotoluene anti-oxidant additive is present.

8. The formulation according to claim 1 , comprising between 1 and 1000 mg/kg of a sulphur or phosphorus containing additive.

9. The formulation according to claim 8 , wherein the sulphur containing additive is represented by the formula

R 1 —(S) a —R 2

wherein:

a is 2, 3, 4 or 5; R 1 and R 2 may be the same or different and each may be straight or branched alkyl group of 1 to 22 carbon atoms, aryl groups of 6-20 carbon atoms, alkylaryl groups of 7-20 carbon atoms or arylalkyl groups of 7-20 carbon atoms.

10. The formulation according to claim 9 , wherein the content of the organic polysulfide is between 50 and 800 mg/kg.

11. The formulation according to claim 1 , wherein the formulation has a sulphur content of below 4 wt %.

12. A process to prepare an electrical oil formulation according to claim 1 , wherein the base oil component is subjected to a clay treatment and wherein the anti-oxidant additive is added after performing the clay treatment.

13. A process according to claim 12 , wherein a copper passivator is added after performing the clay treatment.