Constrained by lack of availability of suitable land the consumption of cotton has leveled off while that of polyester has increased rapidly, the demand for clothes, which are made from cotton is increasing in the highly sophisticated countries. Cotton production is criticised as it is a polluting process and the land could be used for food production in the poor countries. Therefore much attention has been directed towards re-engineering of synthetic fibres aimed at mimicking cotton properties such as breathability, comfort, antistatic and dyeability. Even so world cotton production is still growing slowly; it is expected to increase to 20.1 m tonnes for 2003/04, according to the International Cotton Advisory Committee. It is likely that there will always be a demand for cotton, and more research will be directed to environmentally friendly cotton production, coloration and finishing. Coloration of cotton is carried out by using vat, sulphur, azoic, direct and reactive dyes. Reactive dyes are a very important group of dyestuffs for colouring cotton because of their desirable properties which include unrestricted shade range, ease of application, low cost and good fastness to light, washing and rubbing. When they are applied to cellulose by an exhaustion process, they require relatively high levels of electrolyte (salt) to increase the substantivity of the anionic dyestuff for cellulose and thereby achieve high visual colour yields. Discharge of highly saline effluent is becoming environmentally less acceptable, as increased salinity in rivers upsets the delicate balance of aquatic flora and fauna. Hence some recent developments in cotton dyeing with reactive dyes have focused on reduced salt usage. This thesis evaluates one of the options for low salt cotton reactive dyeing; chemical modification (pre-treatment) of cellulose with cationic agents. This has the effect of eliminating the inherent electrostatic repulsion between the anionic (negative) dye and the fibre, so that the use of electrolyte can either be reduced or eliminated. The (negative) surface charge of cotton was modified to a positive charge by using initially a commercial polymeric cationic fixing agent. The amount of cationic agent applied by an exhaustion technique to a cotton fabric, was quantitatively determined using Congo Red, the method being based on the titration of a known concentration of Congo Red with a solution of the treatment agent. The application of this procedure to determine the exhaustion properties of potential cationic pre-treatment agents for cotton was then studied. The pre-treated cotton was dyed to evaluate the effect of the treatment on both dye exhaustion and fixation under three different sets of dyeing conditions and a comparison was made with untreated cotton dyed conventionally. Lower colour yield, inferior wash and light fastness, shade change, ring dyeing and poor migration (levelness) were obtained on the pre-treated fabric. Therefore, pre-treatment of cotton with polymeric cationic agents was adjudged to be of no further interest. To avoid the technical problems associated with the use of polymeric pre-treatment agents, further modification of cotton was carried out with low molecular weight (monomeric) species. A systematic study of the introduction of different amino groups into cotton, via reaction with a commercially available reactive, water soluble dichlorotriazine agent followed by amination with different amines, was undertaken. Where possible, the characterization of the reaction products was made by using a variety of analytical methods. Once the resulting adducts had been characterised, the dyeing behaviour of reactive dyes on the derived substrate was evaluated. The present study also involved the synthesis and application of other pre-treatment agents, e.g. 2,4-bis(4-sulphophenylamino-)-6-chlorotriazine and dyes with a view to obtaining a better understanding of the causes of the shade changes arising from the use of cationic agents to cotton.

The analytical investigation of several historically important natural yellow and red dye sources is presented, extending previous work on the chemical characterisation of the acid hydrolysed extracts from dyed yarns. The PDA HPLC studies of weld (<i>Reseda luteola</i> L.) dyed yarn extracts found that neither the substrate nor additional steps in the dyeing process significantly altered the relative ratio of the main flavonoid components. Furthermore, their relative photo-degradation rates on the dyed yarns were similar, presenting few problems in the identification of the biological source. In contrast, the relative ratio of the main flavonoid components in dyer’s greenweed (<i>Genista tinctoria</i> L.) dyed yarn extracts was highly dependent on the dyeing process. The PDA HPLC and HPLC ESI MSⁿ investigation of the acid hydrolysed extracts of yarn dyed with the <i>Serratula</i> species, sawwort (<i>Serratula tinctoria</i> L.) and <i>Serratula</i> <i>coronata</i> L., identified their characteristic dyeing components to be luteolin, apigenin, quercetin, kaempferol and 3-O-methylquercetin. Similar studies performed on young fustic (<i>Cotinus coggygria</i> Scop.) dyed yarn extracts identified the main colouring components to be fisetin and sulfuretin. Due to the relatively high photo-degradation rates of many of the characteristic components in both sawwort and young fustic, the identification of historical yarns dyed with these sources was problematic. The dye components characterisic for Mexican cochineal (<i>Dactylopius coccus</i> Costa) were all found to be structurally related anthraquinones, with similar photo-degradation rates on the dyed yarns. Analysis of the principal dye components from brazilwood (<i>Caesalpinia sappan</i> L.) and logwood (<i>Haematoxylon campechianum</i> L.) using negative ion ESI MSⁿ enabled the identification of new, structure dependent, mass spectrometric breakdown pathways. The mechanisms were supported by deuterium labelling experiments and the results were shown to be useful for the structural determination of previously unidentified components. An elimination product observed in the PDA HPLC analysis of hematein dyed yarn extracts was structurally characterised using NMR techniques. A similar component, derived from brazilein, was also observed in brazilwood dyed yarn extracts. A novel approach towards mordant identification using inductively coupled plasma techniques was investigated. ICP MS analysis was successful in identifying the metallic ions present in the acid hydrolysed extracts from both reference and historical yarns. However, interpretation of the results from historical samples was challenging due to the observation of large amounts of both aluminium and iron in the sample extracts. Within the Monitoring of Damage to Historic Tapestries (MODHT) project, yellow and green yarns from a selection of 15^th – 17^th century tapestries were investigated. Analysis of the yarn extracts identified weld and dyer’s greenweed as the most prevalent yellow dye sources, with young fustic frequency identified in the metal thread core extracts.

This thesis is concerned primarily with the use of fluorescence spectroscopy and UV-Vis absorption spectroscopy to study the aggregation of phthalocyanine and orthp-hydroxyazo textile dyes in solution. A preliminary investigation of the use of laser irradiation to induce fading of dyed textiles, as a possible method of assessing light fastness of dyes, is also reported. Fluorescence and UV-Vis spectroscopy have been used to investigate the aggregation of a commercial reactive textile dye, a sulphonated copper phthalocyanine dye, known here as turquoise-1. With very few exceptions, phthalocyanine dimers are found to be non-fluorescent. This thesis reports on the observation of a fluorescent dimer of turquoise-1 in ethanol and water. Fluorescence excitation and emission spectra at room temperature and 77K are presented. These are consistent with the conventional model of exciton coupling in a cofacial dimer. The fluorescence arises from a dimer with a particular geometry, while the majority of dimer species present in solution, which give rise to the characteristic hypsochromically shifted absorption spectrum, are non-fluorescent. Theoretical modelling of extinction co-efficients obtained from aqueous solution of turquoise-1 shows that, in salt-free solutions, aggregates higher than dimers exist. However, in solutions containing high salt concentrations the tendency to form the higher aggregates dramatically decreases. The fluorescence spectra of the monomer and dimer species of a typical ortho-hydroxyazo dye, known here as red~l, are shown to be clearly distinguishable, while their absorption spectra overlap strongly and cannot be resolved. Thus, the aggregation of this dye in aqueous and ethanolic solution is not readily apparent from the absorption spectrum, but is revealed by fluorescence spectroscopy. Fluorescence excitation spectra and emission spectra in water and ethanol, at room temperature and 77K are reported. The effect of increasing the temperature of the dye solution on the extent of aggregation has also been investigated. A number of ortho-hyroxyazo reactive dyes related structurally to red~l have also been investigated. These systems show similar behaviour to red~l and fluorescence spectroscopy is again shown to be a valuable probe of aggregation. Initial studies show that laser irradiation of dyed textile fabrics can be used to induce fading of the dye without damage to the textile fibre. The time taken for laser-induced fading of standard samples of blue-dyed wool is consistent with their light fastness values defined by the international dyestuffs industry. The effect of dye strength on laser-induced fading times is in line with results from conventional light fastness measurements. Cotton dyed with turquoise~l exhibits photochromism on laser irradiation, this is attributed to reversible one-electron reduction of the copper (II) phthalocyanine in the presence of free amine groups on the dyed fabric.

<i>Cis-trans </i>photoisomerisation of 4 simple disperse azo dyes and a series of reactive azo dyes has been studied by ¹H nuclear magnetic resonance (NMR) spectroscopy, with an <i>in situ</i> laser irradiation of the sample. The laser irradiation was coupled into the sample within the NMR magnet <i>via</i> an optical fibre. This enabled the first ¹H NMR measurements to be made of the transient <i>cis</i> isomers of 4-(4-nitrophenylazo)aniline, (Disperse Orange 3), and 4-[N-ethyl-N-(2-hydroxyethyl)amino]-4’-nitroazobenzene, (Disperse Red 1). Typical NMR methods including ¹H 1D, ¹H-¹H 2D COSY and ¹H-¹H 2D EXSY/NOESY, were used to assign ¹H resonances of the <i>trans </i>and <i>cis</i> isomers. <i>Ab initio</i> calculations were used to predict the chemical shifts of <i>cis</i> and <i>trans</i> isomers of the disperse dyes, in good agreement, with the experimental results, and to rationalise the chemical shift changes observed on isomerisation. The technique of NMR with <i>in situ</i> laser irradiation has enabled the examination of the kinetics of <i>cis</i>-<i>trans</i> isomerisation of the series of reactive dyes, showing that the technique has great potential for correlating structure with light fastness properties of dyes. The high resolution of NMR yields unambiguous kinetic information that is currently unobtainable due to the limitations of traditional methods. Calculated minimum energy structures of both <i>cis</i> and <i>trans </i>isomers of a selection of the reactive dyes serve to rationalise experimentally determined kinetics.

The chelates of seven commercial disperse dyes with nickel, copper and chromium have been formed in cotton and in nylon 6 fabrics. Exhaustion dyeing was satisfactory on nylon 6 and subsequent treatment in the metal salt solution at optimum pH was followed by steaming. The cotton was pretreated with a urea/melamine precondensate with glyoxal formaldehyde, and a polyethylene glycol. Dye was introduced by vapor-transfer from coated paper. Chelation was achieved in a final step. The hue and brightness, fastness to Light, washing and perspiration were assessed for the dyed fabrics. The nickel complexes were in general found to be slightly better than the chromium and copper complexes. Photodegeration of the fibres was reduced by the presence of the nickel complexes. Average stabilisation of nylon 6 was found to be 43% and that of cotton 23%. It may be possible to use selected nickel chelates as dyes that stabilise photodegradabLe fibres. The amount of nickel reacting with the dyed cotton fabric was determined by employing atomic absorption spectroscopy.

The cost of energy and present market demand for special dyeing effects have created a situation which has resulted in a number of mechanical innovations designed to change the character of textile dyeing. The present work investigates a novel machinery concept and unconventional continuous dyeing process. The process is accomplished by applying the dye liquor to the fabric using the 'FKO system' (Foster Khaled Oulton). The original concept involves preheating and removal of air from the fabric by saturated and superheated steam under pressure in a continuous manner. After passage through a labyrinth seal, the FKO system heats the ecru fabric using saturated or superheated steam under pressure and the fabric then passes through the dye liquor. When the ecru fabric is presented to the dye liquor, it is hot, swollen and air free. A variety of fabrics have been tested, including cotton, polyester, wool, cotton/polyester and cotton/wool union fabrics. The use of compressed air fed labyrinth seals allows high speed, non-contact expression of surplus liquid. Expression perfonnance is found to be equal to, or better than, that produced by the heaviest available mangle systems and gives more controlled variable expression values. The application of different types of computer feedback control is discussed. Methods for the control of temperature, pH and level parameters of the dye liquor in the FKO system are suggested.

An environmentally friendly route to anthraquinone dyes has been developed by exploiting the anthraquinone biochromophores produced by microorganisms. An extensive screen of biochromophore producers, including species of Pyrenophora, Trichoderma, Drechslera, Phoma and Curvularia, was undertaken. The biochromophores were extracted from the mycelia with acetone and characterised by means of TLC, HPLC, GLC, mass spectrometry and UV /vis spectrophotometry. Most of the organisms produced anthraquinones unsuitable for conversion to anthraquinone dyes/dye intermediates. Problems included the anthraquinones being produced only at low temperatures, being too complex for dye conversion, possessing substitutions in the P-position, or being produced association with fatty material or as mixtures and thus not of high enough purity for dye conversion. Two strains of Curvularia, C. lunata and C. ramosa produced cynodontin (1,4,5,8- tetrahydroxy-3-methylanthraquinone) of the required purity although initial yields were poor and associated with melanin. Strain selection and manipulation of the culture medium resulted in elimination of melanin and cynodontin yields of up to l.0g dm-3. The culture medium developed contains nitrate as the nitrogen source and 6% sucrose as the carbohydrate source. Zinc was shown to influence the balance between anthraquinone and melanin production whilst a cycle of l2h white light/l2h respite from light produced a lO fold increase in cynodontin yield. The optimum pH was pH 7.0 whilst a temperature of 28°C and aeration of around 4 dm3 minot with impeller speed of 400rpm was preferred. Cynodontin, once acceptable as a dyestuff in its own right, no longer has the washfastness required for modern detergents. However, as an intermediate, cynodontin requires only a few simple chemical steps to produce a blue biodye which is an analogue of Disperse Blue 7 and a green biodye which is an analogue of Acid Green 28. Both biodyes appear brighter than their chemically synthesised analogue and also possess slightly better fastness properties than the conventional dyes when applied to knitted polyamide.

No description available.

No description available.

No description available.