Chloro- and bromo-pyranthrone pigment prodn. - by recrystallisation from alkanol, cycloalkanol, alkanone or cycloalkanone

摘要

Prodn. of pigments from pyranthrones of formula (I) (in which A is Cl and n = 0, 1 or 2, or A is H and n = 0, 1, 2, 3 or 4) involves forming (recrystallising) (I), converted to finely-divided form by milling or re-pptn. from H2SO4, in 4-10C alkanols, 6-8C cycloalkanols, 4-10C alkanones and/or 6-8C cycloalkanones, opt. in the presence of water. Forming is pref. carried out in MEK, methyl n-propyl ketone, diethyl ketone, cyclohexanone, iso-BuOH, n-pentanol and/or cyclohexanol at 30-200 degrees C. The pigments, esp. 6, 14-dichloropyranthrone (Ia), satisfy the requirements for application and colour better and give much yellower tones. The transparency of the pigments makes them suitable for use in metal-effect lacquers.