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.
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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
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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
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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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