GB768074A - Improvements relating to natural and synthetic rubber compositions - Google Patents

Abstract

A vulcanized synthetic rubber composition is reinforced with carbon black and silica, the latter having an average particle size of 0.01 to 0.05 micron and a surface area of 50 to 225 square metres per gram and constituting about 15 to 60 per cent by weight of the combined carbon black and silica. The silica is preferably a hydrated silica and may be prepared by reacting a sodium silicate solution with carbon dioxide gas (see Group III). The composition preferably contains an amount of silica which is at least 10 per cent by weight of the rubber. The synthetic rubbers specified are butadienestyrene copolymers such as GRS, and other polymers and copolymers of conjugated diolefins having a high abrasion resistance.ALSO:A hydrated silica having a surface area of 140 to 150 square metres per gram and an average particle size of 0.02 to 0.05 micron for use for reinforcing natural or synthetic rubber (see Group V) is prepared by reacting a sodium silicate solution with carbon dioxide gas. 17,000 gallons of sodium silicate solution, Na2O(SiO2)3.36, containing 20.3 grams of Na2O per litre is maintained at a temperature of 162 DEG to 172 DEG F. whilst a mixture of carbon dioxide, nitrogen, and air containing 10 to 10.8 per cent carbon dioxide is introduced thereinto at a rate sufficient to provide 1,250 cubic feet of carbon dioxide gas per minute (measured at 76 cms pressure and 0 DEG C.). The gas is introduced for 8 1/2 hours directly under a turbo-agitator in the tank containing the sodium silicate solution. After this period the rate of supply of carbon dioxide is reduced to 400 cubic feet per minute and the solution is boiled for 1 1/2 hours by introducing steam thereinto. The slurry is then washed and the silica recovered and dried at 100 DEG to 125 DEG C.ALSO:A vulcanized natural or synthetic rubber composition is reinforced with carbon black and silica, the latter having an average particle size of 0,01 to 0,05 micron and a surface area of 50 to 225 square metres per gram and constituting about 15 to 60 per cent by weight of the combined carbon black and silica. The silica is preferably a hydrated silica and may be prepared by reacting a sodium silicate solution with carbon dioxide gas (see Group III). The composition preferably contains an amount of silica which is at least 10 per cent by weight of the rubber.