GB668724A - Process of making hydrophilic carbon black - Google Patents

Abstract

In compounding natural or synthetic rubber, e.g butadiene-styrene copolymers, a 5-10 per cent aqueous suspension of carbon black, which has been rendered hydrophilic by treatment with an aqueous solution of a hypochlorite of an alkali or alkaline earth metal, is added to produce a stable dispersion, free from dispersing agent, without coagulation and the copolymer is precipitated with 10-35 per cent carbon black dispersed therein by acidifying the dispersion.ALSO:Hydrophilic carbon black is prepared by exothermally reacting furnace, thermatomic, or acetylene black with an aqueous solution of a hypochlorite of an alkali or alkaline earth element, e.g. sodium or potassium. The carbon black may be treated directly with aqueous hypochlorite, or suspended in caustic soda solution through which chlorine is passed, or suspended in an aqueous sodium chloride solution which is electrolyzed. For example carbon black is treated with 10 per cent sodium hypochlorite solution at 35 DEG C and the sludge with pH8-9 is acidified to pH2 by hydrochloric acid. The sodium chloride and excess hydrochloric acid are washed out and the carbon black is separated from the sludge by centrifuging, filtering and partial air drying at below 100 DEG C. The dry product still contains 5 per cent water and may be readily dispersed in water after the addition of a few drops of ammonia. A water paste of the carbon black containing 30-60 per cent water may be used as a lubricant in place of graphite paste.