'Dyeing Performance of Reactive Dyes by Different Continuous Process
Part 1: Effect of Dyes Substantivity and Hydrolysis on Colour yield and fixation'
To determine the most suitable padding method for dyeing on cellulose fabric for a particular group of reactive dyes, two vinyl sulphone reactive dyes containing sulphato ethyl sulphone i.e. Remazol G/Y RNL and Remazol Black B and two monochlorotriazine i.e. Cibacron G/Y P2RN and Cibacron Grey PTGE were applied under two different dyeing methods- Semi Continuous (Pad Batch) and Continuous (Pad Thermofix) method, evaluated the yield by latest version of spectrophotometer (Datacolor SF 650+). It was observed that low substantive dyes show good yield in semi continuous while high substantive dyes give better yield in Pad thermofix. Both methods have good fastness results.
It always is a fascinating to improve the yield and quality of the dyes by introducing new class, modified groups and even the dyeing method. Reactive dyes differ from other class of dyes in term of that the molecule of a reactive dyes contains one or more reactive groups capable of forming a covalent bond with a compatible fibre group. The main step in the dyeing procedure with a dye of such type comprise adsorption on the fibre, diffusion into the fibre and react with the specific group of fibre, by means of nucleophilic addition or nucleophilic substitution. Reactive dyes containing sulphatoethylsulphone give addition reaction, while the dyes containing Cyanuric chloride give substitution reaction in presence of alkali .
Reactive dyes have been very popular due to their high wet fastness, brilliance and range of hues. Continuous dyeing with reactive dyes is now important due to its high productivity and consistency of shades over runs .Continuous Dyeing with reactive dyes, usually done by padding process i.e. Pad thermofix, pad batch and pad steam. In this study the only pad thermofix and pad batch are being discussed. In pad batch process, more dwell time by means of batching is provided to fix the dye into the fibre. In fact it is an exhaust method at extremely low liquor ratio and ambient temperature . The impregnated batch is store separately from padding machine and thus allow wide variation of dwell time according to the dye selected and the pH of the impregnated temperature. Whereas in Pad thermofix method dye is fixed into the fibre by means of high temperature, which shorten the dwell time . Due to variation in yield and fastness properties and feasibility during dyeing, different reactive groups give different yield in different process on the basis of their substantivity and reactivity. In this present work we sought to review the suitable dyeing process for certain reactive group in short liquor.
About the Authors:
The authors are associated with Applied Chemistry Research Centre (Textile Section), PCSIR Laboratories Complex, Off University Road, Karachi, Pakistan.