GB759919A - Process for the production of carbon black pigments - Google Patents

Abstract

Carbon black is subjected, in dispersion in at least twice its weight of water, to disintegration by mechanical means, e.g. stirring mechanism, stirrer type autoclave or kneading machine, while the dispersion is externally heated, preferably to above 100 DEG C., e.g. 130-150 DEG C., under pressure, and solid carbon black is recovered from the dispersion. The aqueous dispersion may contain substances which decompose with gas evolution on heating. In the Examples: (1) a dispersion of carbon black in water, which may contain a wetting agent, is heated in a stirrer autoclave at 138-140 DEG C, and the carbon black is separated from the dispersion and dried (2), (3) carbon black is treated with aqueous ammonia and then with aqueous hydrogen peroxide, or an aqueous dispersion of carbon black containing sodium methyl naphthalene sulphonate is treated with aqueous ammonia and hydrogen peroxide, and the resulting dispersions are heated with stirring to 80 DEG C. and 75 DEG C. respectively, with the result that ammonium nitrite, formed as the result of the action of H2O2 on NH3 is decomposed to nitrogen and water, and the carbon black is separated and dried: (4) an aqueous dispersion of carbon black containing azoisobutylic acid nitrile is heated and stirred at 90 DEG C. with formation of N2, and the carbon black is filtered off and dried. Other decomposable substances referred to are urea nitrile, and hydroxylamine or its nitrite. The treated carbon black, which is preferably that obtained from higher fractions of coal tar, e.g. crude naphthalene, or anthracene oil, or from petroleum products, is suitable as pigment for lacquers and printing inks, has high wetting power and gives oil suspensions of low viscosity.