VS dyes are widely used for exhaust dyeing, cold pad batch process and also in automated batch wise dyeing machines. These are also used for printing by one phase or two phase application method. The range offers very good light and wash fastness. Excellent white effect on dyed grounds by discharge and resist printing method. It has high stability in dry state and neutral solution.
Reactive group:- Reactive Dyes are Vinyl Sulphone based Reactive Dyes having Vinyl sulphone as the reactive group.
Reaction with cellulose
They react chemically under suitable conditions with Cellulose based materials in presence of alkali, these dyes react with the hydroxyl group of cellulose and form firm, covalent linkages, yielding brilliant shades with good fastness properties.
Vinyl Sulphone Base Dyes offer high solubility in water and suitable for both Exhaust/Pad-batch Dyeing and Discharge Printing.
VS' dyestuffs posses poor affinity for cellulosic fibers in absence of salt and alkalis. For this reasons, they are suitable for use on pad. Their substantivity can be increased by addition of glauber salt or common salt and alkali, making the dyestuff suitable on all conventional dyeing machine for loose material, yarn in hanks and packages and piece goods.
Due to their versatile nature dyeing methods may therefore, be classified under the padding and exhaust processes, standing baths are not recommended, as in alkaline medium inactivation of the dyestuffs by reaction with water takes place as a side reaction.
These Dyestuffs are unstable under alkaline condition, and therefore water used for their dissolution should be neutral.
As the Dyestuffs react chemically with Cellulose based materials, the dyed materials posses good fastness properties.
Dyeing and Dyeing Method
It is possible to use mixture of Vinyl Sulphone Base Dyes for getting combination shades. For this application Vinyl Sulphone Base Dyes of similar properties are to be used.
VS Dyes are dissolved by pasting it with a little water and pouring boiling hot water over it under stirring. The water used should be neutral.
DYEING METHOD :
Conventional method Dyeing Cycle
All in one Method
Exhaust Dyeing Method :
1.Take well scoured/bleached material, ensure that pH of the material is below 7.
2.Add predissolved dye and run for 10 min. at 40ºc.
3.Add Common salt in 3 instalments at an interval of 10 min. Raise the temp. to 60ºc in 20 min. and run for 20 min.
4.Add alkali (Soda Ash for light medium and dark shades and mixed alkali soda +caustic for extra dark shades)and run for 1 hour.
Salt & Alkali Requirement for VS Based Reactive Dyes
Salt gpl mercerized cotton
Fixation time in min.
up to 0.10
0.11 - 0.30
0.31 - 0.50
0.51 - 1.00
1.01 - 2.00
2.01 - 3.00
3.01 - 4.00
Neutralize with 1-2 cc/lit. Acetic Acid in cold
Soap at 80 -85 C
Repeat the soaping process again for achieving better fastness propertise.