Cl Reactive Red 3 or, Aminochloro-s-triazine Dyes

Reaction of a dichloro-s-triazine dye with an amine at about 25–40°C  produces a much less reactive 2-amino-4-chloro derivative as exemplified by CI Reactive Red 3. More energetic reaction conditions, typically 80°C and pH 11 for batchwise application, are necessary for efficient fixation on cellulosic fibres. Early studies of the relationships between structure and substantivity of aminochlorotriazine dyes revealed that the NH bridging groups linking the chromogen and the uncoloured arylamino substituent to the heterocyclic ring had marked effects on the solubility and dyeing properties of the dyes. Replacement of the simple NH imino group by an N-methylimino bridge tended to lower the substantivity for cellulose. The use of a sulphonated arylamine to form the uncoloured 2-arylamino substituent of a monochlorotriazine dye was helpful to enhance solubility and modify the dyeing behaviour.