Dyeing cellulosic textile allowing repeated use of dye-bath - by deactivating dyestuff before replenishment to reduce salt loss without impairing dyeing quality

摘要

In dyeing cellulosic textile material with reactive dyestuff (I) from aq. dyebaths an exhausted dyebath is used, in which residual (I) has been deactivated, and replenished with fresh amts. of (I) and any ancillaries needed for reactive dyeing. Residual (I) is deactivated by heating ca. 20-30 deg.C above the dyeing temp. USE/ADVANTAGE - The technique allows repeated use of the dyebath without affecting the dyeing quality and is universally applicable. It avoids increasing the salt consumption and associated costs and increases the fixing yield, i.e. saves (I). Losses and disposal costs are only ca. 5-20% of the usual levels. It is even possible e.g. to use an exhausted bath of red dyestuff for dyeing with a fresh yellow dyestuff, without impairing the quality of the yellow dyeing. 100 kg cotton yarn packages were dyed for 45 min at 45 deg.C with 1000 l aq. dyebath contg. 5 kg of the reactive dyestuff Reactive Red 2 (dichlorotriazine reactive gps.), 70 kg NaCl and 15 kg Na2CO3. 800 l exhausted dyebath were recovered and heated to 80 deg.C to deactivate the residual dyestuff.