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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.
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 SolutionsUnstable 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 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
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 machine
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.