SINGLE-PHASE MIXED CRYSTALS OF LAKED MONOAZO DYES

摘要

Novel improved mixed crystals of monoazo dyes of formula (I), wherein R1 is methyl or chlorine, and R2, R3 and R4 are each independently of the others hydrogen, methyl or chlorine, which dyes have been laked with alkaline earth metal cations and ammonium cations in a molar ratio of about 1 :2. The mixed crystals are single-phase. The products according to the invention, while having a fine particle size, exhibit substantially better fasteness properties than similar known products and are therefore excellently suitable as tinctorially strong pigments. In addition, the part played by after-treatment is less critical. Also claimed is a process for the preparation of a pigment of formula (II), wherein R1 is methyl or chlorine, R2, R3 and R4 are each independently of the others hydrogen, methyl or chlorine, R5, R6, R<7? and R>8< are hydrogen or methyl, and E is Mg, Ca or Sr, by crystallisation from an inert hydrophilic liquid in th epresence of solvated cations E++ and NR>5<R>6<R>7<R>8<?+>, wherein the pigment is a single-phase mixed crystal and x is a number from 0.33 to 0.62 and y is a number from 0.76 to 1.34, and the concentration of solvated cations E++ at the beginning of the crystallisation is higher than the concentration of solvated cations NR5R6R7R8<+>. Three embodiments are disclosed.