Nippon Oil Company

Midori Masunaga

Yoshiki Kohno

Hiroshi Hasegawa

Noboru Ishida

Tadashi Ohmori

Shoji Kimura

Kohji Hayashi

An electrical insulating oil composition consisting essentially of 50-85 parts by weight of a paraffinic or mixed base crude oil-derived electrical insulating oil, 50-15 parts by weight of a naphthenic base crude oil-derived electrical insulating oil, and 0.001-1.0% by weight of a hydrocarbon-derived pour point depressant, based on the total weight of said two oils.

Electrical insulating oil compositions

An electrical insulating oil composition consisting essentially of (I) 50-95 parts by weight of a mineral oil-derived electrical insulating oil, (II) 5-50 parts by weight of at least one oil selected from diarylalkanes, polybutene, an oil having a specified refractive index and a hydrocarbon oil-derived hydrofined oil, and (III) 0.001-1.0% by weight of a hydrocarbon-derived pour point depressant, based on the total weight of the oils (I) and (II).

An electrical insulating oil having excellent oxidation stability, thermal stability, corona resistance and corrosion resistance and, if desired, low-temperature properties, which consist essentially of a blend of a refined oil (I) derived from a paraffin or mixed base crude oil, a refined oil (II) prepared from a lubricating oil fraction of a mineral oil and, if desired, an amorphous ethylene-propylene copolymer (III). The oils (I) and (II) may be blended together in ratios by weight of 80- 99:1- 20. In one embodiment, the copolymer may be added to the blend of the oils (I) and (II) in ratios by weight of 0.001- 1.0 to 100 thereby to obtain an electrical insulating oil having excellent low-temperature properties in addition to the above-mentioned excellent properties.

Electrical insulating oil

An electrical insulating oil composition having satisfactory oxidation stability, electrical properties and low-temperature performances, consisting essentially of (I) an electrical insulating oil having a sulphur content of 0.1-0.35 wt.% prepared from a paraffin or mixed base crude oil and (II) 0.001-1.0% by weight, based on said insulating oil, of an essentially amorphous ethylene-propylene copolymer having an average molecular weight of 10,000-200,000 and a propylene content of 10-70 mol%.

An electrical insulating oil consisting essentially of (1) a mineral oil, as the base oil for the product oil, containing not more than 0.35 wt.% of sulphur and being prepared by refining a distillate containing at least 80 wt.% of a fraction boiling at 230.degree.-430.degree. C at atmospheric pressure, the distillate being obtained by the distillation of paraffin or mixed base crude oils, (2) at least one arylalkane and, if desired, (3) a hydrocarbon-derived pour point depressant.

Electrical insulating oils

An electrical insulating oil having excellent thermal stability and low-temperature properties, which consists essentially of (A) 80-99 parts by weight of refined oil having a low sulphur content and considerable aromatic content and being prepared from a distillate contained in a fraction boiling between 230.degree.-430.degree. C of a paraffin or mixed base crude oil origin, (B) 1-20 parts by weight of a refined oil prepared from a lubricating oil fraction of a mineral oil boiling between 230.degree.-460.degree. C of any crude oil origin and, if desired, (C) 0.001-1.0 part by weight of an essentially ethylene-propylene copolymer as the additive.

An electrical insulating oil having excellent oxidation stability, thermal stability, corona resistance, corrosion resistance and, if desired, a particularly low pour point, which consists essentially of a blend of a refined oil (I) derived from a paraffin or mixed base crude oil, a refined oil (II) prepared from a lubricating oil fraction of a mineral oil, at least one arylalkane (III) such as an alkylbenzene, and, if desired, an essentially amorphous ethylene-propylene copolymer (IV).

This invention provides a method for the preparation of insulating oil having good oxidation stability, electric characteristics and resistance to copper corrosion which comprises subjecting a distillate (stock) within a temperature range from 250.degree. to 400.degree. C. in terms of the boiling point at atmospheric pressure to solvent refining to a desulfurization from 30 to 75% by weight to give a raffinate, said distillate having been obtained either by distillation at atmospheric pressure of a paraffin- or mixture-base crude oil and/or by distillation under reduced pressure of a residual oil from the atmospheric pressure distillation, subjecting said raffinate to hydrogenating refining to a desulfurization from 40 to 90% by weight and subjecting the refined product to solvent dewaxing, and if necessary, subsequently subjecting the dewaxed product to clay treatment to a sulfur content of the final product from 0.1 to 0.35% by weight.

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Tokyo, Japan

Midori Masunaga