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Reactive Dyeing Process: Vinylsulphone or Vinyl Sulfones:
These reactive groups are normally transients, and are masked by water solubilizing leaving groups and their name is abbreviated to VS. The Vinyl sulfone groups are actually written as -SO2-CH=CH2,
but we cannot find this group in actual dye-bath. What we may see is:
-SO2-CH2-CH2-OSO3-(H+ or Na+),
depending up on the pH.
This VS group has the following disadvantages against its new counter parts such bifunctional dyes, HE dyes etc.
Low efficiency of fixation to the fiber (40 to 50%)
Highly colored effluent discharge
High dosages of salt and alkali
The Dyeing Procedures:
Vinyl sulphone dyes may be applied using any one
of the following methods according to the substrate quality machinery available
and final quality requirements of the dyed material. In some cases, even a difficult
shade like purple, olives, grays and metameric browns require special process
sequences.
Cold Dyeing Process
Hot Dyeing Process
All in one method
Isothermal Process
Temperature increasing process
Cooling
Method of dyeing
For any one of the application, we have to set
the dye bath with suitable auxiliary chemicals as may be required for the
purpose of maintaining the dyeing conditions throughout the length of the
process.
The following recipe suggests a sharpening dye
bath, which you may alter according to your conditions.
Dye bath Sharpening Recipe:
a. Acetic Acid 0.30 to 0.50 gram/liter
b. Sequestering Agent 0.5 to 1.00 gram/liter
c. Leveling Agent 0.5 to 0.75 gram/liter
d. De-foaming Agent * 0.1 to 0.3 gram/liter
e. Lubricating Agent 0.25 to 0.4 gram/liter
f. Mono sodium Phosphate ** 0.20 to 0.25 gram/liter
More
on Reactive Dyeing:
Vinylsulphone Dyeing - Basic Requirements
Vinylsulphone dyestuff - Color Index Number, Fastness properties, Dischargeability
Preconditioning Method of Reactive Dyeing - 20% more depth, 20% Steam Saving and improved wash fastness properties!
Softflow Dyeing machine - Cleaning and Loading procedure
Uneven Dyeing in Softflow machines - reasons and tips
Influence of pH on Reactive dyeing
How to make tonal corrections during dyeing? What is the right way?
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