GB557321A - Cable oil and insulating material impregnated therewith - Google Patents

Abstract

557,321. Hydrocarbons ; electric insulation. FIFE, J. G: (Shell Development Co.). April 8, 1942, No. 4623. [Class 2 (iii)] An electrical insulating cable oil consisting essentially of a mixture of poly tertiary alkyl naphthalenes substantially free from primary and secondary alkyl radicals is formed by reacting naphthalene with tertiary base olefines such as isobutylene, diisobutylene, triisobutylene, methisobutylenes, the product of polymerizing isobutylenes with sulphuric acid (hot acid octylenes), tertiary alkyl chlorides, and tertiary alcohols in the presence of a Friedel- Craft or other alkylating catalyst. The ratio of alkyl radicals to naphthalene should be greater than 2 and preferably between 3 and 5. Mixtures of oils are produced which are then subjected to high vacuum fractional distillation to produce fractions boiling respectively below and above 200‹C. at 3 mm. mercury. The lower fractions have a low viscosity index and a dielectric strength of about 35-40 kV. The heavier fractions have a very low viscosity index, being extremely viscous or semi-solid at ordinary temperature and very fluid at slightly elevated temperature, and a dielectric strength of about 50 kV. According to examples, naphthalene is reacted respectively with hot acid octylenes and with diisobutylene in the presence of aluminium chloride and the products fractionally distilled at a pressure of 3 mm. to give products having a viscosity index varying from 65 to -418 and a dielectric strength of about 40 kV. The residues from the distillation were further distilled at lower pressures down to 0.05 mm. giving products of viscosity index about -1230 and dielectric strength about 50 kV.