Electric cables and compositions for use in them

Claim 1

A fully-filled telecommuncation cable comprising a plurality of metallic conductors each coated with cellular insulation and a sheath enclosing said conductors and containing a filling medium comprising (by weight): (a) 70-98% of a hydrocarbon base comprising: (i) a first component which is selected from the group consisting of mineral oils, petroleum jellies and mixtures of mineral oil with wax; (ii) a second component which is soluble in the first component and which comprises at least one hydrocarbon whose molecules are substantially incapable of diffusing into polyethylene, polypropylene and other cellular insulating material at temperatures of up to 80° C., its number average molecular weight being low enough and its quantity sufficient to establish an osmotic pressure relative to that of the first component as solvent, which is effective to inhibit migration of said first component into cells of said cellular insulation; (b) 1-15% of a block copolymer which comprises a main polymer chain made up of repeating units of at least two kinds covalently bonded together, said repeating units being non-randomly distributed along the length of said chain in such a way as to divide said chain into at least one block tending to confer solubility in the base and at least one block tending to inhibit such solubility, the proportions of the blocks being such that the polymer forms a gel with the base; and (c) 1-15% of a hydrocarbon material that is miscible with said base and said block copolymer above 135° C. but forms solid dispersed particles at a temperature not lower than 65° C.