Cationic thiadiazolyl triazene dyestuffs

A cationic triazene dyestuff of the formula ##STR57## wherein B is alkylmercapto, arylmercapto or ##STR58## R is hydrogen, alkyl, alkenyl, C.sub.1 -C.sub.4 -alkylcarbonyl, benzoyl, benzoyl substituted by halogen or C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxycarbonyl, mono-C.sub.1 -C.sub.4 -alkylaminocarbonyl, di-C.sub.1 -C.sub.4 -alkylaminocarbonyl, benzylaminocarbonyl, C.sub.1 -C.sub.4 -alkylsulphonyl, phenylsulphonyl, di-C.sub.1 -C.sub.4 -alkylaminosulphonyl, cycloalkyl, aryl, aralkyl, amino, alkylamino, dialkylamino, arylamino or aralkylamino,

• R.sub.1 is hydrogen, alkyl, alkenyl or aralkyl, or
• R and R.sub.1 together with the nitrogen atom to which they are bonded are pyrrolidine, piperidine, morpholine, piperazine, N-methyl-piperazine or N-hydroxyethylpiperazine,
• R.sub.2 and R.sub.3 each independently is alkyl, alkenyl, alkynyl or aralkyl, or one of them is hydrogen, or
• R.sub.3 is bonded to the o-position of A, and together with the nitrogen atom and A is dihydroindole, tetrahydro-1,4-benzoxazine which is unsubstituted or substituted by 1-4 C.sub.1 -C.sub.4 -alkyl or C.sub.1 -C.sub.4 -alkoxy,
• A is aryl, and
• An.sup.(-) is an anion,
• or a substitution product thereof wherein the cyclic and acyclic radicals are substituted by cyano, hydroxyl, halogen, nitro, alkyl, monoalkylamino, dialkylamino, phenyl, alkoxy, alkoxycarbonyl, alkoxcarbonyloxy, C.sub.1 -C.sub.4 -alkyl-carbonyloxy or carboxyl;
• or R-R.sub.3 is substituted by phenoxy, benzyloxy or amidocarbonyl.