Improvements in or relating to tyres

摘要

For use in tyre manufacture (see Group XXXIV), silicone rubber is reinforced with glass cords, the individual filaments of which are coated with a cured organosiloxane having an average of from 1.9 to 2 monovalent hydrocarbon or halogenated hydrocarbon radicals per silicon atom. Suitable silicone rubbers comprise those in which the organic radicals are attached to the silicon through silicon-carbon linkages, the radicals being any hydrocarbon radical such as methyl, ethyl, vinyl, allyl, cyclohexyl, octadecyl, cyclohexenyl, tolyl, phenyl, xenyl, or benzyl, or any halogenated hydrocarbon radical such as trifluorovinyl, chlorphenyl, bromophenyl, trifluorotolyl, perfluorocyclobutyl, pentafluoroethyl, and chlorocyclohexyl. The organic groups may also comprise functional groups such as hydroxyl, carboxyl, nitrile and amide. Suitable fillers such as fume silica, silica aerogel, carbon black, metal oxides and calcium carbonate may be used in the mix together with setting-agents such as mercuric oxide, zinc peroxide and metallic zirconates, and oxidation inhibitors and pigments. The glass cords are prepared from drawn filaments, of from 0.0002 to 0.0004 inch diameter, which are passed through the organosilicon coating composition and then stranded into bundles of about 200 filaments and heated as necessary to 115-400 DEG C. for about 5-10 minutes to cure the silicone coating. The strands are then spun into threads and the threads twisted into a cord of the desired size, the finished cord receiving a cured coating in the same manner as the filaments. The coating composition may be applied in liquid form by dipping or spraying. Suitable siloxanes for the coating composition, which may comprise a dispersion in a solvent such as xylene, include dimethylsiloxanes, phenylmethylsiloxanes, dibutylsiloxanes, and copolymers of dimethylsiloxane and monomethylsiloxane, of a ,a ,a -trifluorotolylmethylsiloxane and dimethylsiloxane, of vinylmethylsiloxane and tolylmethylsiloxane, of dimethylsiloxane monophenylsiloxane and octadecylmethylsiloxane, and of chlorophenylmethylsiloxane and dimethylsiloxane. Fillers such as silica, aerogels, fume silicas, titania, clay and carbon black may be employed, and the siloxanes are preferably cured on the filaments by use of an organic peroxide such as aromatic acyl or benzoyl peroxides or tertiary butyl per-benzoate. A typical dispersion comprises 15 per cent of a mixture of 100 parts of dimethylpolysiloxane gum, 35 parts of fume silica and 7 1/2 parts of benzoyl peroxide in 85 per cent of xylene. The coated cords are partially embedded, in parallel relation, in a sheet of uncured silicone rubber such as a mixture of 100 parts of dimethylpolysiloxane gum with 35 parts of fume silica and 3 parts of benzoyl peroxide, and the sheet then partially cured. Uncured silicone rubber comprising 100 parts of a copolymer of 92.4 mol. per cent of dimethylsiloxane, 7.5 mol. per cent phenylmethylsiloxane and 0.1 mol. per cent vinylmethylsiloxane, with 50 parts of fume silica, 4 parts of ferric oxide and 1 part of benzoyl peroxide is then calendered on to the exposed cords, and the resultant laminate bias-cut to provide tyre plies.