Condensation products of melamine, (benzo) triazoles and aldehydes

A compound of formula I ##STR14## wherein A is ##STR15## R.sub.1 is hydrogen, C.sub.1 -C.sub.20 alkyl, C.sub.2 -C.sub.20 alkenyl, C.sub.5 -C.sub.12 cycloalkyl, or C.sub.5 -C.sub.12 cycloalkyl which is substituted by C.sub.1 -C.sub.10 alkyl;

• phenyl, naphthyl;
• phenyl or naphthyl, each of which is substituted by C.sub.1 -C.sub.10 alkyl, C.sub.1 -C.sub.10 alkoxy, halogen, hydroxy, nitro or phenoxy;
• a group of formula ##STR16## wherein R is hydrogen or C.sub.1 -C.sub.10 alkyl, and Z is oxygen, Schwefel, --NH--, --NR.sub.6 -- or a methylene group,
• or R.sub.1 is COOR.sub.7,
• R.sub.2 is hydrogen, C.sub.1 -C.sub.20 alkyl or C.sub.5 -C.sub.12 cycloalkyl,
• R.sub.3 is hydrogen, C.sub.1 -C.sub.5 alkyl, C.sub.1 -C.sub.5 alkoxy, hydroxy, halogen, nitro, carboxy or C.sub.2 -C.sub.11 alkoxycarbonyl,
• R.sub.4 and R.sub.5 are each independently of the other --SH, --NH.sub.2, --NHR.sub.6, --NO.sub.2, --COOH, --SR.sub.6, --N(R.sub.6).sub.2, --COO--R.sub.6 or maleimido,
• R.sub.6 is C.sub.1 -C.sub.10 alkyl,
• R.sub.7 is hydrogen, M.sup.n+ /n or [NR.sub.8 R.sub.9 R.sub.10 R.sub.11 ].sup.+,
• M is alkali or alkaline earth metal, n is 1 or 2, and
• R.sub.8 to R.sub.11 are each independently of one another hydrogen, C.sub.1 -C.sub.8 alkyl or C.sub.1 -C.sub.8 hydroxyalkyl.