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The dyes were first introduced by Hoechst, based on ß-sulphato ethyl sulphone as a reactive group. The range made the successful breakthrough due to comprehensive shade range, versatile application, ability to be dyed at 60°C and good compatibility with other bifunctional dyes. Being a compact structure, it offers ease in wash off for removal of unfixed dyes at the end of dyeing during washing. The dye fibre bond offers good acid stability. With the limitations to above, there may be problems with reproducibility associated with it, which is not accepted especially for pale shades. There is the possibility of unlevel dyeing with a small variation in the process due to its lower molecular weight.
General Characteristics of reactive hetro bifunctional dyes:
Hetro bifunctional dyes made a get through in early 80's. The dyes were based on a quite simple but beautiful chemistry. They had filled a big vacuum of various hues of bright shades, which were not possible with vinyl sulphone type. The dyes were conventional Dichlorotriazine type, with the end condensation of ß-sulphato ethyl sulphone to have different type of reactive group in a single molecule. Being a dual reactive, the primary mode of fixation is from vinyl sulphone group and the dyeing temperature is same as vinyl-sulphone, which enables good intercompatibility in between the two classes.
Reactive dyes have the following typical characters
| Solubilizing Group |
Chromophore |
Bridging Group |
Reactive Group |
| Makes the dye soluble in water |
Gives the dye its color |
Joins the reactive group to the chromophore |
Reacts with fiber molecule to form a covalent bond |
| Eg.
Sulphonic groups |
Azo, Azo metal complex dyes and phthalocyanine and anthraquinone |
-NH-
-CH2-N-CH3 |
Monochlrotriazine,
Dichlorotriazine,
Monochlorovinylsulphone,
Bismonochloroatrozine vinylsulphone |
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