Improvements in or relating to self-bonding insulating tapes for use in jointing electric cables insulated with butyl rubber-base compositions and to cables joined therewith

摘要

Self-bonding insulating tapes for rebuilding the insulation in the jointing zone of electric cables insulated with a butyl rubber base composition are formed from compositions prepared by mixing together butyl rubber and carbon black, by heating them in the presence of a promoting agent to obtain bonding of the two materials, and thereafter incorporating with the product so obtained an adhesive agent capable of imparting a surface tackiness to the tapes, said promoting agent comprising para-quinone dioxime, dibenzo-para-quinone dioxime, N-methyl-N.4-dinitrosoaniline or poly-para-dinitrosobenzene and said adhesive agent comprising a polymer obtained by the condensation of aromatic hydrocarbons with formaldehyde or low molecular weight substituted polystyrene. The compositions may also comprise calcined clay, paraffin wax, stearic acid, zinc oxide and conventional vulcanizing ingredients such as sulphur, para-quinone dioxime, dibenzo-para-quinone dioxime and red lead. The adhesive agents may be those sold under the trade names "Kenflex" and "Piccolastic", and the preferred carbon black is a gas black of high surface reactivity, e.g. SRF, EPC or MPC.