Verfahren zur Herstellung von Disazopigmenten

Method of producing a disazo pigment, in which a coupling reaction is carried out while feeding, into an acidic aqueous solution, a tetrazo aqueous solution containing a tetrazo component of benzidines and a coupler aqueous solution containing a coupling component, wherein the coupling component is a mixture comprising a main component represented by the formula (1): CH3COCH2CONH-X, wherein X represents a phenyl group optionally having one or the same or different plural substituents selected from the group consisting of a methyl group, methoxy group and chlorine atom; a first additional component represented by the formula (2): CH3COCH2CONH-Y, wherein Y represents a phenyl group having a substituent selected from the group consisting of -CONR2 group, -SO2NR2 group and -NHCOR group, and the phenyl group may further have a substituent selected from the group consisting of a methyl group, methoxy group, chlorine atom, -CONR2 group, -SO2NR2 group and -NHCOR group, and wherein Rs may be the same or different mutually, and represent a hydrogen atom, C1 to C4 alkyl group (the alkyl groups may be mutually connected to form a ring) or C1 to C4 alkylene NR'2, further wherein R's represent a hydrogen atom or C1 to C4 alkyl groups which may be mutually different (the alkyl groups may be mutually connected to form a ring); and, a second additional component represented by the formula (3): CH3COCH2CONH-Z, wherein Z represents a phenyl group substituted by any one of a carboxyl group or alkali metal salts thereof, hydroxyl group or sulfonic acid group or alkali metal salts thereof, and said phenyl group may further has a substituent selected from the group consisting of a methyl group, methoxy group, chlorine atom, carboxyl group or alkali metal salts thereof, hydroxyl group or sulfonic acid group or alkali metal salts thereof. According to the method, disazo pigments can be obtained which manifest excellent transparency and flowability of the inks produced therefrom, and excellent flushing property and flushing drain coloration resistance in the pigment production process, or excellent dispersibility when ink is formed under dry condition.