The Design, Synthesis and Application of Easy Wash Off Reactive Dyes

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Title: The Design, Synthesis and Application of Easy Wash Off Reactive Dyes
Author: Suwanruji, Potjanart
Advisors: Peter J. Hauser, Committee Member
Leonard Stefanski, Committee Member
Harold S. Freeman, Committee Chair
David Hinks, Committee Member
Abstract: Reactive dyes are colorants used mainly on cotton to achieve high washfastness on leisurewear. The basis for their good washfastness is the formation of a covalent bond to cellulose chains during the fixation step. Unfortunately, fiber fixation is always accompanied by alkali-induced dye hydrolysis, leading to dye molecules that cannot undergo fixation with cellulose. After the dyeing step, effective wash off of unreacted dye is required to obtain excellent fastness properties. It is well known that reactive dyes having low substantivity exhibit low percent fixation but good wash off properties in the hydrolyzed form. On the other hand, reactive dyes having high substantivity show high fixation but poor wash off properties in the hydrolyzed form. Since many of the more modern and environmentally friendly reactive dyes fall into the latter category, it was deemed of interest to design new dyes that not only give high fixation levels but also reactively low substantivity in the hydrolyzed form. As a consequence, the wash off process would be easier to complete. The present study involved lowering the substantivity of the hydrolyzed dye by reducing the coplanarity that is usually required between dyes and cellulose for high substantivity. In this regard, reactive dyes were synthesized. Specifically, bis-dichlorotriazine (bis-DCT) bifunctional and bis-monochloro triazine/bis-sulphatoethylsulphone (bis-(MCT/SES)) tetrafunctional reactive dyes were made (cf. dyes 1-20). The dyes were applied to cotton fabric using pad-batch, pad-dry-cure, and exhaust dyeing methods. Bis-DCT bifunctional reactive dyes were applied to cotton by a pad-batch method, since the dichlorotriazine reactive groups are highly reactive and can be applied at room temperature. Bis-(MCT/SES) tetrafunctional reactive dyes were applied to cotton by pad-dry-cure since monochlorotriazine reactive groups require higher temperatures for fixation. The exhaust dyeing method was not suitable for these reactive dyes because of their low water solubility. Evaluation of colorfastness on dyed cotton showed that the fabrics had moderate to good colorfastness to rubbing and laundering, and had low colorfastness to light.
Date: 2004-08-02
Degree: PhD
Discipline: Fiber and Polymer Science
URI: http://www.lib.ncsu.edu/resolver/1840.16/4342


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