MONOAZO LAKE PIGMENT

PURPOSE:To provide the title pigment which is red and gives printing ink or paints having excellent clarity, tinting power, gloss and resistance to water and heat, consisting of a novel beta type crystal form having an X-ray diffraction pattern totally different from that of alpha type crystal. CONSTITUTION:A diazo component obtd. by diazotizing an amine of formula I at not higher than 5 deg.C, is coupled with a coupler component obtd. by dissolving an acid of formula II is an aq. NaOH soln., at not higher than 5 deg.C to obtain a monoazo dye of formula III. A suspension of the dye is heated at 20-45 deg.C, and an aq. soln. of a Ba salt is added thereto. The mixture is reacted at not higher than 45 deg.C to form a lake, thus obtaining the title pigment having betatype crystal form, represented by formula IV and characterized by an X-ray diffraction pattern with high diffraction intensity at an angle of diffraction (2+ or -0.2 deg.; Cu-Kalpha) of 5.0 deg., medium diffraction intensity at an angle of diffraction of 25.0 deg. and relatively low diffraction intensity at angles of diffraction of 14.8 deg. and 19.5 deg..