| 摘要 |
<p>1516223 Laked azo dyestuffs HOECHST AG 30 Jan 1976 [30 Jan 1975] 03760/76 Heading C4P A laked azo compound is prepared by reacting a diazotizable amine (aromatic or heteroaromatic) with the stoichiometric amount of a nitrite and of a coupling component at - 10‹ to + 80‹C in water in the absence of added acid, at least one of the reaction components containing at least one free acid group capable of lake formation and subsequently laking any free acid group remaining in the product. As long as there is at least one free acid group, other acid groups may be laked before or during the coupling. The nitrite may be an alkali metal nitrite or the nitrite of a metal which is capable of forming lakes e.g. Ba, Mn, Ca or Sr. A buffer substance may be present in the coupling mixture, or a base to adjust the pH to a suitable value. A minor proportion of a water-miscible organic solvent may also be present, and a surface active agent may be added. The laked azo compound may be used to colour a plastic material e.g. PVC or a printing paste for use in graphic printing.</p> |
