Modified form of a disazo pigment

摘要

The disazo pigment of the formula CHARACTERIZED BY A SPECIFIC SURFACE OF 12 - 20, PREFERABLY 13 - 18 M2/G, A MAXIMUM OF THE DISTRIBUTION OF THE GRAIN SIZES OF BETWEEN 500 AND 1000 NM AND A PROPORTION OF THESE GRAIN SIZES IN THE TOTAL DISTRIBUTION OF BETWEEN 35 AND 65 %. This disazo pigment is obtained by isolating the pigment, after coupling, by stirring it out with alkali and, after having filtered it and washed it to neutrality, heating it to temperatures above 100 DEG C in a mixture of water and a solvent which is immiscible with water or miscible with water to a limited degree only.