Process for the continuous reaction of cyanuric fluoride with sulfo-containing aromatic amines

A process for the continuous reaction of cyanuric fluoride with amines, which comprises passing cyanuric fluoride and an aqueous solution of an aminonaphthalenesulfonic acid simultaneously and continuously into a flow reactor, performing thorough mixing there, then passing the reaction mixture into a second reactor in which there is only little back-mixing but good radial mixing, and completing the reaction there, wherein the reaction is carried out at 0.degree. to 50.degree. C. and at a pH between 1 and 8, and wherein the conversion in the first reactor is at most 50%.