CRINA TURCAS, ION SEBE<br>Synthesis and Characterization of Some New Azo Dyes <br>for Synthetic and Artificial Fibres

CRINA TURCAS, ION SEBE
Synthesis and Characterization of Some New Azo Dyes
for Synthetic and Artificial Fibres

Abstract:

This paper presents the synthesis of direct azo dyes derived from benzotriazole, according to the following succession of reactions diazotisation of 4-amino-3-nitrotoluene, coupling with cresidine, m-toluidine, m- xylidine and 1-aminonaphthalene reduction and cyclisation leading to a triazolic heterocycle, sulphonation and oxidization. All the stages followed the synthesis procedures found in the literature. The dyes were obtained in high yields, in different shades of yellow. They have variable tinctorial properties, are resistant to lacquers, to dry friction and less resistant to humid friction. The dyes which can be applied on wool have a red colour. They are not soluble in water, but, at high temperatures, become soluble in alkaline medium. At a low temperature, the dyes are soluble in methanol-ethanol solutions and they can be used to dye cotton - like cellulose fibres and previously bleached woollen fibres. In order to validate the azoic structure of the synthesized dyes, we have studied their suspension in neutral and alkaline medium at high temperatures, when they were reduced with sodium hydrosulphite and reoxidized with K2S2O6. The dyes absorb in UV-Vis at wavelengths ranging from 430 to 500 nm. After being applied on the fibres, we tested their reaction to wet treatments via reapplication with potassium dichromate and aniofix. If the suspension is reduced with sodium hydrosulphite and is exposed to air, the colour fades. This behaviour is specific to azo dyes which are not soluble in water in a neutral medium. Keywords: direct azo dyes, benzotriazole, cresidine, 4-amino-3- nitrotoluene, m- toluidine, m- xylidine, 1- aminonaphthalene

Issue: 2010, Volume 61, Issue 9

Pages:

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