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.Listed below are some of the parameters and questions that a dye manager must consider before opting for any dyeing process.
Common Dyeing Problems
- 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
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 Solutions Unstable dye dispersion
Incorrect dyeing program
- Select dyes that has better dispersion stability
- Application of efficient dispersant
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 fibre
- Catalytic fading because of unsuitable dye combination
Pale areas found after dyeing is over
- Repeat thermofixation (at high temperature)
- Selection of appropriate dyes
- Adjustment of dye selection
Deviations in shades of dyeing causes can be-
- Proper ventilation of vapours and gases
- Avoidance of contact with dangerous substances
- Sensitivity of dyes to hydrolysis, reduction, electrolyte
- Sensitivity of dyes to metal ions in the dye bath
Presence of Precipitates in the dye bath
- Selection of dyes very carefully, exact control of pH
- Giving attention to stability of dye with respect to electrolytes
- Causes can include crystallization of dyes due to changes in temperature in the dye bath
- Usage of volatile carriers
Poor dye fixation
- Using systems that has perfect liquor circulation
- Selection of suitable carriers, usage of overhead heating in the machine
System losses in continuous dyeing processes
- 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.
- 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.