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» Buyers Guide to Dyes
Buyers Guide to Dyes
Dyeing is a very critical process and ensuring
the quality of dye is also very critical. The warm and moist conditions are
also an important factor that should be considered while dyeing any product.
In this competitive world 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
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 opted 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 chosen or not
Common Dyeing Problems
A Dyer encounters a lot of problems while dyeing the
products. Here in this page a few of such common dyeing problems as faced by
the dyer are discussed along with solutions.
|Common Dyeing Problems
|Unstable dye dispersion
- Select dyes that has better dispersion stability
- Application of efficient dispersant
|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
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 fibre
- 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 dye bath
- Selection of dyes very carefully, exact control of pH
- Giving attention to stability of dye with respect to electrolytes
|Presence of Precipitates in the dye bath
- Causes can include crystallization of dyes due to changes in
temperature in the dye bath
- Usage of volatile carriers
- Using systems that has perfect liquor circulation
- Selection of suitable carriers, usage of overhead heating in the
|Poor dye fixation
- This has been a common problem particularly with reactive dyeing
when it comes to batch dyeing of cellulose fibres. This can be taken
care of by the use of sophisticated molecular engineering
techniques. Use of Bi-functional and low-salt reactive dyes can
attain more than 95% fixation rate even for cellulosic fibres.
- 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.