Prepn. of conc. solns. of stilbene azo dyes - by alkaline condensn. of 4-nitrotoluene 2-sulphonic acid

摘要

Conc. solns. of direct-exhausting stilbene azo dyes are made by alkaline condensn. of 1 mol 4-nitro toluene 2-sulphonic acid (I), opt. together with 4,4'-dinitro stilbene disulphonic acid (II), and opt. in presence of reducing agent, using 1.1-3 mols reaction prod. of ammonia, ethylene oxide and water. Also the stilbene azo dyes obtd. contg. at least one SO3H gp. neutralised by the above reaction prods. Used for dyeing of paper or cotton in greenish-yellow to orange shades. The solns. contg. 10-50 wt.% dye are stable and do not crystallise or flocculate during prolonged storage under fluctuating conditions. They can be used without further treatment, opt. after dilution with water.