Electrical insulating oils

Claim 2

An electrical insulating oil consisting essentially of (I) 100 parts by weight of a mineral oil (A) having a sulphur content of not higher than 0.5 wt. %, a pour point of from -10° to -25° C. and a nitrogen content of not more than 100 p.p.m., the mineral oil (A) being prepared by subjecting at at least to hydrofining and solvent dewaxing a fraction containing a distillate having a boiling range of 280° - 400° C. at atmospheric pressure, the fraction being obtained by the distillation of a paraffin base crude oil or a mixed base crude oil and (II) 5- 100 parts by weight of a highly aromatic hydrocarbon oil (B) prepared by hydrofining a fraction having a boiling range of 250° - 400° C. at atmospheric pressure, the fraction being produced as a by-product of subjecting naphtha hydrocarbons to reforming reaction at temperatures of 400° - 600° C. in the presence of a catalyst selected from the group consisting of the Platinum Group metals and combinations of each of the Platinum Group metals with at least one of Ge, Sn, Re, Fe, Ni, Pb and halogens.

Claim 3

An electrical insulating oil consisting essentially of (I) 100 parts by weight of a mineral oil (A) having a sulphur content of not higher than 0.2 wt. %, a pour point of from -10° to -25° C. and a nitrogen content of not more than 100 p.p.m., the mineral oil (A) being prepared by subjecting at least to hydrofining and solvent dewaxing a fraction having a boiling range of 280° - 400° C. at atmospheric pressure, the fraction being obtained by the distillation of a paraffin base crude oil or a mixed base crude oil, (II) 5- 30 parts by weight of a highly aromatic hydrocarbon oil (B) prepared by hydrofining a fraction having a boiling range of 250° - 400° C. at atmospheric pressure, the fraction being produced as a by-product of subjecting naphtha hydrocarbons to reforming reaction at temperatures of 400° - 600° C. in the presence of a catalyst selected from the group consisting of the Platinum Group metals and combinations of each of the Platinum Group metals with at least one of Ge, Sn, Re, Fe, Ni, Pb and halogens, and (III) 1- 15 parts by weight of a refined oil (C) prepared by treating the lubricating oil fraction of a mineral oil with a solid absorbent.

Claim 4

An electrical insulating oil consisting essentially of (I) 100 parts by weight of a mineral oil (A) having a sulphur content of not higher than 0.2 wt. %, a pour point of from -10° to -25° C. and a nitrogen content of not more than 100 p.p.m., the mineral oil (A) being prepared by subjecting at least to hydrofining and solvent dewaxing a fraction having a boiling range of 280° - 400° C. at atmospheric pressure, the fraction being obtained by the distillation of a paraffin base crude oil or a mixed base crude oil, (II) 5- 30 parts by weight of a highly aromatic hydrocarbon oil (B) prepared by hydrofining a fraction having a boiling range of 250° - 400° C. at atmospheric pressure, the fraction being produced as a by-product of subjecting naphtha hydrocarbons to reforming reaction at temperatures of 400° - 600° C. in the presence of a catalyst selected from the group consisting of the Platinum Group metals and combinations of each of the Platinum Group metals with at least one of Ge, Sn, Re, Fe, Ni, Pb and halogens, and (III) 1- 15 parts by weight of a refined oil (C) prepared by treating the lubricating oil fraction of a mineral oil with a solid absorbent.

Claim 5

An electrical insulating oil according to claim 1, wherein the hydrocarbons to be subjected to the reforming reaction are those boiling in the range of 60° - 200° C.

Claim 6

An electrical insulating oil according to claim 2, wherein the hydrocarbons to be subjected to the reforming reaction are those boiling in the range of 60° - 200° C.

Claim 7

An electrical insulating oil according to claim 2, wherein the lubricating oil fraction as the material for the refined oil (C) is one having a boiling range of 230° - 500° C.

Claim 8

An electrical insulating oil according to claim 1, wherein the highly aromatic hydrocarbon oil (B) contains not less than about 50% by weight of about C 10 to about C 18 bicyclic and monocyclic aromatic hydrocarbon.

Claim 9

An electrical insulating oil according to claim 1, wherein the highly aromatic hydrocarbon oil (B) contains not less than about 90% by weight of about C 10 to about C 18 bicyclic and monocyclic aromatic hydrocarbon.

Claim 10

An electrical insulating oil according to claim 2, wherein the highly aromatic hydrocarbon oil (B) contains not less than about 50% by weight of about C 10 to about C 18 bicyclic and monocyclic aromatic hydrocarbon.

Claim 11

An electrical insulating oil according to claim 2, wherein the highly aromatic hydrocarbon oil (B) contains not less than about 90% by weight of about C 10 to about C 18 bicyclic and monocyclic aromatic hydrocarbon.

Claim 12

An electrical insulating oil according to claim 6, wherein the highly aromatic hydrocarbon oil (B) has a specific gravity of d 4 20 0.980- 1.000, a refractive index of n d 20 1.56- 1.60 and a specific dispersion of 220- 240.

Claim 13

An electrical insulating oil according to claim 7, wherein the highly aromatic hydrocarbon oil (B) has a specific gravity of d 4 20 0.980- 1.000, a refractive index of n d 20 1.56- 1.60 and a specific dispersion of 220- 240.

Claim 14

An electrical insulating oil according to claim 8, wherein the highly aromatic hydrocarbon oil (B) has a specific gravity of d 4 20 0.980- 1.000, a refractive index of n d 20 1.56- 1.60 and a specific dispersion of 220- 240.

Claim 15

An electrical insulating oil according to claim 9, wherein the highly aromatic hydrocarbon oil (B) has a specific gravity of d 4 20 0.980- 1.000, a refractive index of n d 20 1.56- 1.60 and a specific dispersion of 220- 240.

Claim 16

An electrical insulating oil according to claim 1, containing 8- 50 parts by weight of highly aromatic hydrocarbon oil (B) per 100 parts by weight of mineral oil (A).

Claim 17

An electrical insulating oil according to claim 1, wherein mineral oil (A) has a sulphur content higher than 0.2 wt. %.

Claim 18

An electrical insulating oil according to claim 2, wherein the refined oil (C) has a sulphur content of about 0.1- 2 wt. %.

Claim 19

An electrical insulating oil according to claim 2, wherein the refined oil (C) has a sulphur content of about 0.2- 1.5 wt. %.

Claim 20

An electrical insulating oil according to claim 2, containing not higher than 0.35 wt. % sulphur.

Claim 21

An electrical insulating oil according to claim 18, containing 0.05 to 0.3 wt. % sulphur.

Claim 22

An electrical insulating oil consisting essentially of (I) 100 parts by weight of a mineral oil (A) having a sulphur content of not higher than 0.5 wt. %, a pour point of from -10° to -25° C. and a nitrogen content of not more than 100 p.p.m., the mineral oil (A) being prepared by subjecting at least to hydrofining and solvent dewaxing a fraction containing a distillate having a boiling range of 280° - 400° C. at atmospheric pressure, the fraction being obtained by the distillation of a paraffin base crude oil or a mixed base crude oil and (II) 5- 100 parts by weight of a highly aromatic hydrocarbon oil (B) prepared by hydrofining a fraction having a boiling range of 250° - 400° C. at atmospheric pressure, the fraction being produced as a by-product of subjecting naphtha hydrocarbons to reforming reaction at temperatures of 400° - 600° C. in the presence of a Group VIII noble metal catalyst.

Claim 23

An electrical insulating oil consisting essentially of (I) 100 parts by weight of a mineral oil (A) having a sulphur content of not higher than 0.5 wt. %, a pour point of from -10° to -25° C. and a nitrogen content of not more than 100 p.p.m., the mineral oil (A) being prepared by subjecting at least to hydrofining and solvent dewaxing a fraction containing a distillate having a boiling range of 280° - 400° C. at atmospheric pressure, the fraction being obtained by the distillation of a paraffin base crude oil or a mixed base crude oil and (II) 5- 100 parts by weight of a highly aromatic hydrocarbon oil (B) prepared by hydrofining a fraction having a boiling range of 250° - 400° C. at atmospheric pressure, the fraction being produced as a by-product of subjecting naphtha hydrocarbons to reforming reaction at temperatures of 400° - 600° C. in the presence of a Group VIII noble metal catalyst.

Claim 24

An electrical insulating oil consisting essentially of (I) 100 parts by weight of a mineral oil (A) having a sulphur content of not higher than 0.2 wt. %, a pour point of from -10° to -25° C. and a nitrogen content of not more than 100 p.p.m., the mineral oil (A) being prepared by subjecting at least to hydrofining and solvent dewaxing a fraction having a boiling range of 280° - 400° C. at atmospheric pressure, the fraction being obtained by the distillation of a paraffin base crude oil or a mixed base crude oil, (II) 5- 30 parts by weight of a highly aromatic hydrocarbon oil (B) prepared by hydrofining a fraction having a boiling range of 250° - 400° C. at atmospheric pressure, the fraction being produced as a by-product of subjecting naphtha hydrocarbons to reforming reaction at temperatures of 400° - 600° C. in the presence of Group VIII noble metal catalyst, and (III) 1- 15 parts by weight of a refined oil (C) prepared by treating the lubricating oil fraction of a mineral oil with a solid adsorbent.

Claim 25

An electrical insulating oil consisting essentially of (I) 100 parts by weight of a mineral oil (A) having a sulphur content of not higher than 0.2 wt. %, a pour point of from -10° to -25° C. and a nitrogen content of not more than 100 p.p.m., the mineral oil (A) being prepared by subjecting at least to hydrofining and solvent dewaxing a fraction having a boiling range of 280° - 400° C. at atmospheric pressure, the fraction being obtained by the distillation of a paraffin base crude oil or a mixed base crude oil, (II) 5- 30 parts by weight of a highly aromatic hydrocarbon oil (B) prepared by hydrofining a fraction having a boiling range of 250° - 400° C. at atmospheric pressure, the fraction being produced as a by-product of subjecting naphtha hydrocarbons to reforming reaction at temperatures of 400° - 600° C. in the presence of Group VIII noble metal catalyst, and (III) 1- 15 parts by weight of a refined oil (C) prepared by treating the lubricating oil fraction of a mineral oil with a solid adsorbent.