PROCESS FOR PREPARING WATER-SOLUBLE AZODYES Russian patent published in 1994 - IPC

FIELD: varnish and paint industry. SUBSTANCE: the process for preparing water-soluble azodyes for wool, leather, polyamide, natural silk and wood. Water- soluble azodyes are prepared by suspending 4,4-diaminodiphenyl-2,2- disulfoacids in water treated with a magnetic field having an intensity of 30 to 260 kA/m for 0.2 to 1.6 s, diazotizing/4,4-diaminodiphenyl-2,2-disulfoacid, sodium nitrite (2 moles) being added in two stages, first in an amount essential for dissolution of 4,4-diaminodiphenyl-2,2-disulfoacid (1.4-1.9) followed by mixing it with hydrochloric acid (2 or 3 moles) and adding the remaining amount of sodium nitrite, combining with azo-containing compounds such as benzene, naphthalene or methylphenyl pyrazolone and recovering the desired product by drying the dye suspension. The invention makes it possible to use alkali agents for the dissolution of 4,4-diaminodiphenyl-2,2-disulfoacid, reduce the excess of hydrochloric acid and rule out the separation and filtration stages. EFFECT: improved properties of water-soluble azodyes. 3 cl