SYNTHESIS AND DYEING PROPERTIES OF METALLISABLE AND NON METALLISABLE ACID DYES

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Date
2000-05
Authors
YAKUBU, Mohammad Kabir
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Abstract
The research thrust of this thesis investigated the role of acetylation on the colour and dyeing properties of mono azo dyes where H-acid was used as coupling component. It also studied the potentiality of 2-nitroso-l-naphthol both as a pigment when used as a ligand with some selected heavy metals and as a dye to nylon and wool substrates with a possibility of being postmetallized with some metallic salts. In addition, characterization and dyeing properties of dyes where p-amino toluenesulphon-N-ethylanilide was used as diazo component was investigated. In the first case, H-acid was acetylated. Two sets of dyes were synthesized from this and the unacetylated intermediate by coupling with different diazo components. The two groups were characterized and then applied to wool and nylon 6.6 fabrics and their color fastness assessed. Generally, the acetylated dyes gave hypsochromic effects on color. However, color fastness to wet treatments such as washing and perspiration was improved on both substrates as a result of acetylation. Whereas, a general improvement was made on acetylated dyes when applied to wool fabric, no noticeable improvement on light fastness with respect to nylon 6.6 was observed. 2-Nitroso-1-naphthol was synthesized and coupled to two diazo components under alkaline condition. The three compounds were in turn complexed to several heavy metals. Two types of pigments the 1:1 and 1:2 were identified. In the 1:1, one molecule of the organic compound was complexed to one atom of the metal whereas in the 1:2, two molecules of the organic compound were complexed to one atom of the metal. The results showed that both the parent nitroso and its azo derivatives are strong ligands. They formed complexes by mere shaking the solution of the nitroso with an aqueous solution of the heavy metals. However, unlike the complexes derived from the nitroso phenols, the two types of complexes cannot be differentiated by solubility. Similarly, the two types of complexes seemed to absorb at basically the same region. The complexes from different metals gave distinct color differences. Following the success of this, we extended the range of diazo components to increase the number of azo dyes. Their uv-visible and ir-spectroscopies were studied. The dyes obtained were applied to wool and nylon 6.6 fabrics. The kinetics and thermodynamics of dyeing were quantified. The postmetallisability of the dyed substrates with heavy metals was then investigated. The effect of pH on adsorption by wool and nylon 6.6 substrates confirmed that acid-dyeing mechanism could explain the dyeing system. Overdyeing phenomenon observed with the dyeing of polyamide fibres with conventional acid dyes was however, not indicated by these dyes. A dyeing mechanism from this observation was proposed. As with many cases in the literature, thermodynamic and kinetic of dyeing didn't outline any general trend with respect to the influence of molecular size, volume and the degree of sulphonation etc. The dyed substrates proved metallisable with the aqueous solutions of heavy metals. The influence of pH on metallisation showed that the best region is between the pH of 7-9. It also indicated that a very short liquor ratio is more desirable with a very di lut e solutions of the metals. The distinct shade changes confirmed that the nitroso and hydroxyl groups are still intact in their relative positions and therefore formed the complexes in situ. These findings added yet another post metallisable dye in addition to the already existing ones. Its characteristics are however, similar to the dyes with salicylic acid residue. The dyeings showed moderate to excellent wet fastness treatments, but poor light fastness ratings on both substrates, the effect of post metallisation showing l ittle influence. p-Aminololucnesulphon-N-ethylanilide was diazotised and coupled to five different coupling components. After uv-visible and ircharacterisations, the dyes were applied to wool and nylon 6.6 substrates. Thermodynamic and kinetic parameters were quantified together with wet and light fastness indices. The results showed that tautomcrism greatly affected the extinction coefficients of the dyes. The wash and perspiration fastness ratings were also good. The light fastness properties of the dyes were moderate on nylon 6.6 but ranged from good to excellent on wool substrate.
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Being a thesis submitted to the postgraduate School in partial fulfilment of the requirements for the award of Doctor of Philosophy (Ph.D) in Textile Science and Technology, Ahmadu Bello University, Zaria. Department of Textile Science and Technology, Faculty of Science, Ahmadu Bello University, Zaria. May, 2000
Keywords
SYNTHESIS,, DYEING,, METALLISABLE,, NON METALLISABLE,, ACID DYES
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