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Buyers Guide to Dyes
Buyers Guide to Dyes
In today's 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 also 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 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 choosen or not.
What exactly is 'Right First Time' Dyeing?
'Right first time' is a decisive term in dyeing
process. It refers in getting the right shade of fabric the first time
without the uncalled for need to re-shade or washing off to reduce the depth
of shade. It has many advantages:
- Reduction in pollution because of less dye in the effluent
- Considerable savings in terms of energy, labour and reprocessing
- Increased productivity as there is no question of re-processing, so
adequate time to dye more production
Common Dyeing Problems
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
|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
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 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
|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 Bifunctional 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
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