Dyeing is a very critical process. In this
competitive market reliable, cost-effective products and latest
technological solutions are essential for survival. A lot of factors go
in making the dyeing process the right one that not only saves capital
for the dyer but takes care of the environmental problems associated
with dyeing as well.
Listed below are some of the parameters and questions that a dye
manager must consider before opting for any dyeing process.
- Is the process compatible with all the dyes he has opoted for
- If the process is exactly compatible with the machine with
respect to temperature, pH, and material construction and that there
is adequate control of these necessary parameters.
- The chosen dye gives all the fastness requirements as specified.
- Correct dye bath is choosen or not
A Dyer encounters a lot of problems while as he takes
on the dyeing process. Here in this page a few of such common dyeing
problems as faced by the dyer is discussed along with solutions.
Common Dyeing
Problems |
Solutions |
Unstable dye dispersion |
- Select dyes that has better dispersion stability
- Application of efficient dispersants
|
Incorrect dyeing program |
The answer lies in optimization of dyeing process. Which means
adjustment of the process parameters in a manner so that the entire
operation takes place in the shortest possible time. It should not
exceed the tolerance limits with respect to reproducibility and
levelness.
This effectively means quick heating in the temperature ranges
where the dye exhausts slowly or is already exhausted. Controlled
heating as the dye starts showing a particularly high rate of
exhaustion. |
Poor light fastness Causes are:
- Traces of carrier residues on fabric
- Staining of adjacent fiber
- Catalytic fading because of unsuitable dye combination
|
- Repeat thermofixation (at high temperature)
- Selection of appropriate dyes
- Adjustment of dye selection
|
Pale areas found after dyeing is over |
- Proper ventilation of vapours and gases
- Avoidance of contact with dangerous substances
|
Deviations in shades of dyeing
causes can be-
- Sensitivity of dyes to hydrolysis, reduction, electrolyte
- Sensitivity of dyes to metal ions in the dyebath
|
- Selection of dyes very carefully, exact control of pH
- Giving attention to stability of dye with respect to
electrolytes
|
Presence of Precipitates in the dyebath
- Causes can include crystallization of dyes due to changes in
temperature in the dyebath
- Usage of volatile carriers
|
- Using systems that has perfect liquor circulation
- Selection of suitable carriers, usage of overhead heating in
the machine
|
Poor dye fixation |
- This has been a common problem particularly with reactive
dyeing when it comes to batch dyeing of cellulose fibers. This
can be taken care of by the use of sophisticated molecular
engineering techniques. Use of Bifunctional and low-salt
reactive dyes can attain more than 95% fixation rate even for
cellulosic fibers.
- Application of hot rinsing methods
|
System losses in continuous dyeing processes |
- Carrying out of the impregnation step in a nip
- The capacity of the dip trough to be minimized.
- Separate streams in dispensing the dyestuff and auxiliaries.
|