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Sep 8, 2011

Utilizing Bifunctional reactive dyes for reactive printing.

Utilizing Bi functional reactive dyes for reactive printing.

Chemistry of dyes which are used in reactive printing is different from other classes. Among them one is MCT (Mono chlor Triazine), A dye having single chlorine attached to functional Triazine.
This Chemistry of dyes (MCT) provided better fastnesses, Specially washing fastness ISO 105 CO3, Dipping fastness. 

A common practice is to use other family of reactive dyes in printing although this fulfills the task and advantages associated with this phenomena are 
1) cheap/Economical dyes. 
2) Bulk amount available 
3)Nearly same shade depth and tone 

But, disadvantages are poor fastnesses. Commonly in use dyes for reactive dyeing includes bi functional dyes including new generation high built dyes. These dyes have high fixation values and percentage of hydrolyze dye in dye bath is quite low but these dyes can not stand on with alkaline medium for longer period of time

Stock paste used for printing include alginate, mild oxidizing agent, urea and above all quite huge quantity of soda ash (25g/Kg), which is recommended for fixation of reactive dyes in printing. As, already mentioned these dyes are not quite good with alkaline medium when left for longer period of time. So, when these dyes are mixed with stock paste and not printed soon or after immediate addition. These start to hydrolyze and lose up its strength and tone. Temperature work as catalyst here. Temperature effect inversely to the hydrolyzation. More the temperature more quickly dye is going to hydrolyze. As, major areas of Pakistan are hot and quite hardly hit in summer. So, for this experiment 50°C is chosen to check the hydrolyzation rate of bi functional and Purely MCT dyes.
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New high built dyes(again bifuctional ,with Floro triazine group) have very good light fastness. So, some time when light fastness requirement is high and could not be obtained with MCT’s than a common practice is to add to one primary color or change whole recipe from MCT to high build dyes. Again care should be taken when bifunctional dyes are chosen for printing specially considering stability and on some occasions ground staining may occur.

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1 comment:

  1. Can you notify the use of Heat activated priting additive in reactive printing with Binder??


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