Level dyeing in a jet with reactive dyes
What are some important points for achieving level dyeing in jet dyeing with reactive dyes?
In jet dyeing, proper control of the exhaustion rate is achieved by,
-Incremental dosing of salt, simply 1/10, 2/10, 7/10, each in 10 min. intervals.
-In cheese dyeing machines or short -time dyeing cycle in jets, salt is added at once at the start of dyeing before dyestuff. In this case, isothermal dyeing program is adopted, because a higher dyeing temperature during primary exhaustion promotes the migration of dye.
-A proper leveling or migrating time should be elapsed after salt-dye addition. 30-45 min. interval is required for proper leveling.
- pH of the dye bath should be around 6.5 in order to prevent fixation.
-Dosing of alkali should be controlled very precisely, especially in first 20 min. pH should not exceed 9. So addition of soda ash as- 1/100, 1/10, 2/10. Rest at 10 min. intervals is recommended. If pH rises very quickly, during first period, it is rather hard to improve un-leveling, especially in Blue R, Turkis G, beige, gray and khaki shades, un-leveling is unavoidable
-Alkali should not be dosed over long period of time, because dye hydrolyzed and hence washing fastness decreases
-Final approached pH should be around 11, if not, sodium hydroxide or liquid alkali can be supplied in the last 10 min. intervial of soda dosing period.
-Always add soda and alkali in fresh water.