| abstract |
A process for the manufacture of pigments of the formula ##STR1## where ##STR2## is a radical of barbituric acid or of one of its derivatives and ##STR3## is a divalent radical of benzene, 1,2- or 2,3-naphthalene, pyridine or pyrazine, which radical may be unsubstituted or substituted by halogen, alkyl of 1 to 10 carbon atoms, phenyl, carbamoyl, alkylcarbonylamino (where alkyl is of 1 to 17 carbon atoms), benzoylamino, alkoxy of 1 to 4 carbon atoms or phenoxy, the number of substituents being 1 or 2, by condensing amino-imino compounds or bis-imino compounds of the formula ##STR4## where R' and R" may be identical or different and are hydrogen, alkyl of 1 to 4 carbon atoms, hydroxyalkyl of 2 or 3 carbon atoms, phenylalkyl of 7 or 8 carbon atoms or phenyl, with barbituric acid or its derivatives, in the molar ratio of 1:2, in water in the presence of aliphatic carboxylic acids, aromatic carboxylic acids, aliphatic sulfonic acids, aromatic sulfonic acids, mineral acids or mixtures of these, at a pH of from 1 to 6, at from 20° to 150° C. The compounds I are obtained in high yield and good purity. These pigments are readily dispersed and give brilliant yellow colorations of good fastness to light and weathering. |