Level dyeing in a jet with reactive dyes

 

Question:
What are some important points for achieving level dyeing in jet dyeing with reactive dyes?

Answer:
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.