Effect of a cationising agent on the conventional reactive dyeing of cotton

Cationisation of cotton is emerging as an effective tool that may help to solve the environmental problems associated with the dyeing of cotton with reactive dyes. The efficiency of the cationising agent CA200 has been investigated and was found to be more effective when compared with the usual method for reactive dyeing of cotton. Pretreatment of the cotton fabric with the cationising agent increases the rate of dyeing compared with the existing method of reactive dyeing. The colour yields, in terms of the Kubelka–Munk values as a function of the amount of dye fixed, showed that cationisation enhances the colour strength. It also improves the washing fastness, rubbing fastness and depth of shade. The positive environmental impact of this cationisation process is significant and the cationised cotton shows a similar fabric quality as with the normal dyeing process.     

Optimization of high performance m‐aramid fiber with disperse dye containing high color strength

This study focuses on the optimization of parameters involved in the process of dyeing such as temperature, concentration of dye, and swelling agent for m‐aramid fibers with disperse dyes and these parameters were used to investigate the shade depth and fastness properties of m‐aramid fibers. Experiments were carried out in batch system to study the effect of factors and their levels mainly on shade depth of the fibers. The shade depth, that is, K/S value of m‐aramid fibers was improved proportionally with the increasing concentration of swelling agent and dye concentration.     

The enhanced cationic dyeability of ultraviolet/ozone‐treated meta‐aramid fabrics

Aramid fabrics were photo‐oxidised by ultraviolet/ozone irradiation. The surface properties of the modified fabrics were characterised by reflectance, attenuated total reflectance, electron spectroscopy for chemical analysis and surface zeta potential. The ultraviolet irradiation caused the oxygen content of the aramid fabric surface to increase, with the appearance of carbonyl and hydroxyl groups, and reduced the surface zeta potential, coupled with improved water wettability. Moreover, the crystalline structure did not change after ultraviolet/ozone treatment according to X‐ray diffraction results. The modified aramid fabrics showed higher affinity to cationic dyes, which may have resulted from the newly introduced electrostatic interaction between cationic dyes and anionic dyeing sites on the photo‐oxidised surface layers. Although colour fastness to both staining and rubbing were good to excellent, colour fastness to shade change was moderate. Furthermore, the ultraviolet/ozone pretreatment and cationic dyeing of aramid fabrics may overcome the loss in the mechanical properties associated with previously recommended dyeing methods for aramid fabrics.     

Antioxidant‐assisted coloration of wool with xanthophylls extracted from corn distillers’ dry grain

Xanthophylls extracted from corn distillers’ dry grain were successfully applied to dye wool fabrics. As a readily available and cost‐effective grain processing byproduct, corn distillers’ dry grain contains appreciable amounts of isolable xanthophyll colourants, which can potentially be used in textile coloration. However, the application of xanthophylls as textile colourants has been limited, possibly owing to their hydrophobic nature and lack of stability at higher temperatures. In the present work, dyeing of wool fabrics with xanthophyll dyes was performed in the presence of a solubilising agent (diglyme) and an antioxidant (butylated hydroxytoluene). Dyeing conditions were modelled and optimised by the one‐factor‐at‐a‐time method and response surface methodology. Depth of shade of the wool fabrics dyed with 0.33 g l^?1 of xanthophylls could be as high as 10.9 ± 0.5, while the colour fastness to laundering and crocking was better than grade 4. The prominent effect of butylated hydroxytoluene on depth of shade (K/S) was further studied using functionally and structurally related model compounds. The K/S‐enhancing ability of butylated hydroxytoluene was found to be a synergistic result of its antioxidising and complexing abilities. Lab‐extracted xanthophylls of various purities were applied to wool fabrics using the optimised dyeing and aftertreatment conditions. Depth of shade but not colour fastness was significantly affected by the impurities in xanthophylls extracted from corn distillers’ dry grain. The strategy developed by this work not only extends the scope of xanthophyll application into textile coloration but also could be used for other hydrophobic and unstable natural colourants.     

Differential dyeing of wool fabric with metal‐complex dyes after ultraviolet irradiation

Experiments were conducted to investigate the ultraviolet irradiation of wool fabric as a pretreatment for differential dyeing. Wool fabric was irradiated using a medium‐pressure mercury lamp in order to obtain, on the irradiated area, increased dye uptake under the same dyeing conditions as untreated wool. The chemical modification of the fibre surface as a result of ultraviolet irradiation was confirmed by an increase in metal ion absorption and hydrophilicity, in agreement with Fourier Transform‐infrared–attenuated total reflectance spectra, although scanning electron microscopy showed that the fibre morphology was unaffected. A selection of 1:1 metal‐complex dyes was used to show the maximum colour difference between irradiated and untreated areas of the fabric. The experiments focused on two effects: a double face with the same shade but different depths (greater depth on the treated side), and a double face with different shades. The latter effect was achieved by dyeing the irradiated fabrics with mixtures of acid and metal‐complex dyes. Rubbing and washing fastness evaluations at 50 °C confirmed that the dyeings after irradiation with the selected 1:1 metal‐complex dyes scored identically to conventional dyeings.     

The study of colour fastness of commercial microencapsulated photoresponsive dye applied on cotton,cotton/polyester and polyester fabric using a pad‐dry‐cure process

Commercial microencapsulated photoresponsive dye was applied on cotton, polyester/cotton and polyester fabric using a pad‐dry‐cure process. Colour fastness of the photoresponsive fabrics to washing, wet cleaning, dry cleaning, rubbing and light was investigated. The CIELAB colour values of the fabrics before and after testing were measured using a reflectance spectrophotometer, and the colour differences were calculated to evaluate the fastness properties. The fabrics had better colour fastness to wet cleaning and washing than to dry cleaning. The fabrics showed higher colour fastness to wet than to dry rubbing. The photoresponsiveness of the fabrics decreased with prolonged exposure time to artificial light due to low photostability of the microcapsules.     

Structural and dyeing properties of aramid treated with 2‐phenoxyethanol

In this study, 2‐phenoxyethanol was used as a carrier to realise the bright‐colour dyeing of aramid fibre. Fourier transform infrared, X‐ray diffraction, and thermal analyses were used to characterise the modification of 2‐phenoxyethanol on the aramid fibre structure. The dyeing performance, including the K/S value and the dye uptake, was tested by varying the concentration of 2‐phenoxyethanol and related experimental parameters. Structural analysis suggests strengthened H‐bonds, lower crystallinity, and slightly lower thermal stability after 2‐phenoxyethanol treatment, which can be explained by the swelling effect of 2‐phenoxyethanol, enlarging the amorphous structure through the reassembly of hydroxyl bonding to the aramid fibre. The dyeing performance can be improved by increasing the dyeing time, the temperature, and the concentration of sodium nitrate under slightly acidic condition. Colour fastness tests showed that 2‐phenoxyethanol treatment does not affect the rubbing fastness but lowers the wash fastness slightly. Dyeing of aramid is crucial under special environmental conditions in which the products must withstand a harsh environment while retaining a bright colour.     

Influence of liquor ratio and amount of dyestuff in producing ultradeep black dyeing using mercerised and cationised cotton

Cationised cotton allows the dyeing of cotton fabrics without salt and up to 100% anionic dye utilisation. The employment of cationised cotton in the dyeing of high depths of shades with reactive dyes holds marked potential for sustainable improvements through less dye consumption, decreased water usage, and zero salt utilisation, all while obtaining shade depths darker than possible with conventional reactive dyeings. This work builds upon previous work in obtaining ultradeep dyeings of cotton utilising cationised and mercerised cotton by investigating the effects of liquor ratio in dyeing and amount of dye applied. Surprisingly, for mercerised only cotton fabric, it was found that nearly equivalent depths of shade, as indicated by L*, were obtained, irrespective of the liquor ratio and the amount of CI Reactive Black 5 applied from 7% to 10% owf. However, the strengths of the dyeings, indicated by the K/S sum, show slight increases with increasing amounts of dye, but not when the liquor ratio is lowered. Similarly, for mercerised‐cationised cotton, the liquor ratio had a negligible effect on the depth of shade obtained, but increasing the amount of CI Reactive Black 5 resulted in an increase in shade depth and colour strength. Very deep shades with high colour strength were obtained with mercerised‐cationised cotton that were not obtainable with uncationised cotton, even at a very low liquor ratio and with a drastic increase in the amount of CI Reactive Black 5.     

Reactive dyeing of silk using commercial acid dyes based on a three‐component Mannich‐type reaction

Acid dyes are employed for commercially dyeing silk, which results in ionic bonds between the silk fibroin and the dye. This generally leads to low wet fastness properties for dyed silk fabrics. In this work, three commercial acid dyes with aromatic primary amine structures were selected to dye silk using a Mannich‐type reaction, resulting in improved wet fastness of dyed silk by forming covalent bonds between silk fibroin and dye. The Mannich‐type reactive dyeing was applied to silk fabrics at both 30 and 90°C in trials. Dyeing at 90°C can shorten the dyeing time compared with dyeing at 30°C, even although dye exhaustion and relative fixation at 90°C were a little lower. The dyeing process was optimised when the dyeing temperature was 90°C, dyebath pH 4, dye‐to‐formaldehyde ratio 1:30 and holding dyeing time 60 minutes. The results showed that the dye exhaustion on silk fabrics for the three aromatic primary amine‐containing acid dyes exceeded 94% and their relative fixation was over 80%. Their washing and rubbing fastness reached grade 4 or higher. Hence, the colour fastness properties of dyed silk fabrics using the Mannich‐type reactive dyeing method is superior to the conventional acid dyeing method using the same aromatic primary amine‐containing acid dyes. The Mannich‐type reactive dyeing for silk fabrics at 90°C can be developed into a novel and rapid reactive dyeing method, promising an effective dyeing process with excellent colour fastness.     

One‐step dyeing of polyethylene terephthalate fabric,combining pretreatment and dyeing using alkali‐stable disperse dyes

In the conventional dyeing process, polyester and its blended fabrics are usually dyed in a weak acidic medium. In order to reduce cost and improve production efficiency, a new dyeing method – one‐step dyeing of polyethylene terephthalate fabrics, combining pretreatment and dyeing in alkali conditions – was investigated. The alkali‐stable disperse dyes Red 900, Red 902, Yellow BROB and Blue 825 were used to dye polyethylene terephthalate fabrics. The dyeing properties of polyethylene terephthalate fabrics in the case of one‐step dyeing at various pH values or sodium hydroxide concentrations were discussed in terms of colour yield, colour parameters and fastness. The performance of one‐step dyeing using alkali‐stable disperse dyes was excellent. The dyed fabric had good fastness. Wet processing could be combined and shortened. One‐step dyeing of polyethylene terephthalate fabrics could reduce the consumption of water and energy and improve production efficiency. One‐step dyeing of polyethylene terephthalate has potential application in cleaner textile production.     

The quasi‐yarn‐dyed effect: triple dyeing of woven polyester/cationic dyeable polyester/viscose rayon blend fabrics by chemical treatments in the laboratory and on a pilot and an industrial scale

The aim of this study was to carry out triple dyeing of woven polyester/cationic dyeable polyester/viscose rayon blend fabrics with the required colour fastness and physical properties. The feel and final appearance of the fabric were achieved by partial removal of the viscose rayon moiety of the fabric through optimised causticisation treatments. The results of the triple dyeings obtained from laboratory and small‐scale experiments were successfully scaled up in authentic processing equipment. The final product, which has a yarn‐dyed effect, readily satisfied the requirements related to the colour fastness and physical properties.     

An alternative natural dye,almond shell waste: effects of plasma and mordants on dyeing properties

In this study, the effect of the plasma process and the possibility of replacing metallic mordants with plasma treatment were investigated in natural dyeing with almond shell waste as a novel natural colorant. The use of a smaller amount of metallic mordants and plant than most of the current natural dye applications is a major advantage of dyeing with almond shell extract. Plasma‐treated and untreated wool fabrics were dyed without mordant and using a smaller amount (0.2 g/l) of alum, iron(ii ) sulfate and copper(ii ) sulfate. Three mordanting methods, namely premordanting, simultaneous mordanting and post‐mordanting, were applied. Colour measurements and light and wash fastness values were compared. Significant colour differences were observed among the mordanting methods. Simultaneous mordanting resulted in the lightest colours with all the mordants. Generally, post‐mordanting produced duller colours and lower a* and b* values than premordanting. The plasma process generated significant colour value differences and colour yield increases, giving more homogeneous dyeing visually, and also ensured a greater impact of mordanting. However, compared with metallic mordants, plasma itself did not create completely different colour shades and fastness improvement. It was necessary to use mordants in order to achieve increased fastness properties (especially light fastness) and a different colour gamut.     

Mathematical relationship between the colour shade depth and the fibre count for disperse dyeing of polyester fibres

The colour shade depth of dyed microfibres is lighter than that of dyed conventional fibres even if there is no difference between the absorbed dye quantities ( M _t) within the fibre. This difference is due to the different light reflectance on the fibre surface for microfibre and conventional fibre, which have a different specific surface area. In this study, the simple mathematical relationship between the colour shade depth, the fibre counts (0.22, 0.56 and 1.46 dtex) and the adsorbed dye quantity is developed for disperse dyeing. The experimental dyeing results and the obtained dyeing results from the simple mathematical relationship were compared for different fibre counts.     

Synthesis and application of a novel,triphendioxazine‐based,phosphorus‐containing acid dye for wool

A novel phosphorus‐containing acid dye based on triphendioxazine was designed and synthesised from diphenylamine through a series of reactions. The dye has a navy‐blue colour, high molar extinction coefficient of 5.32 × 10⁴ l/mol·cm, and high substantivity for dyeing wool in a salt‐free, aqueous dyebath. A high exhaustion value of 98.2% on wool fabrics was recorded at 3% omf and a liquor ratio of 1:20. The wash fastness values of the acid dye, including colour change and staining on cotton and wool, were grades 5, 4 and 4–5, respectively. The dry and wet fastness are grades 4–5 and 4, respectively. In addition, light fastness reaches grades 6–7 at 3% omf dye concentration. These dye properties are better than those of commercial triphendioxazine dyes, for example, CI Direct Blue 106 and CI Reactive Blue 198, under analogous dyeing conditions.     

Dyeing and fastness properties of benzodifuranones, naphthodifuranones and naphthofuranonepyrrolidones

Dyeings were carried out on polyester with benzodifuranones, naphthodifuranones and naphthofuranonepyrrolidones (which had been synthesised previously) to study dyeing properties. Symmetrically and asymmetrically substituted naphthodifuranones showed poor dyeing properties in terms of dyeing and fastness. Asymmetrically substituted red benzodifuranones showed excellent dyeing properties and fastness. Asymmetrically substituted blue benzodifuranones showed good dyeing properties; however, the colour hue was dull and the light fastness was inferior. The naphthofuranonepyrrolidones showed similar dyeing and fastness to those of symmetrically substituted naphthodifuranones, but the colour hue was duller.     

Dyeing and fastness properties of phthalimide‐based alkali‐clearable azo disperse dyes on poly(ethylene terephthalate)

The properties of a series of phthalimide‐containing azo disperse dyes and azo dyes with N‐methyl phthalimide moieties in their diazo component were investigated and compared when used to colour polyethylene terephthalate. The N‐substitution of the phthalimide gave a hypsochromic effect on the colour change and better colour yields on poly(ethylene terephthalate) fabrics, probably because of the electron‐donating property of the methyl group and the higher hydrophobicity of phthalimide‐containing azo dyes compared with those containing phthalimide moieties. The results show that phthalimide‐based azo disperse dyes have excellent dyeing fastness properties and that high wash fastness can be achieved using alkali clearance. This alternative clearance method is important for reducing the environmental impact of the dyeing process by replacing reductive clearing and, in particular, by removing the need for sodium hydrosulphite, which creates a high biological oxygen demand when released in conventional disperse dyeing effluent and which generates aromatic amines.     

Rope dyeing of fabric in supercritical carbon dioxide for commerical purposes

A novel method for fabric rope dyeing in supercritical carbon dioxide fluid has been successfully developed for the first time for commercial purposes by employing a custom‐built machine. The influence of parameters such as system pressure, temperature, and dyeing time on fabric colour strength was investigated, and the parameters optimised. Moreover, the level dyeing property, reproducibility, and colour fastness were investigated and evaluated under various conditions. The carbon dioxide recycling efficiency and the running costs of the proposed process in comparison with conventional processes for commercial production purposes were also investigated. The rope dyeing results show significant influence of the process parameters on fabric colour strength. Satisfactory and commercially acceptable products with a good level dyeing property, high reproducibility of coloration, and good fastness, rated at 4–5 or 5 for washing and rubbing, were obtained with supercritical carbon dioxide fluid. Moreover, a carbon dioxide recycling efficiency ranging from 92 to 95.2% was possible. In comparison with conventional dyeing processes, running costs were lowered by employing the proposed process and rope dyeing machine.     

Deep‐coloured polyester/cotton blends with low concentrations of polymethylol dyes by a one‐pass continuous dyeing process

An obvious limitation of the one‐pass continuous dyeing process for polyester/cotton blends is its inability to achieve deep colour depth, which is caused by the low dye fixation yields of commercial reactive dyes. In this study, the performances of polyester/cotton blends dyed with high‐fixation polymethylol dyes and disperse dyes were compared with those of polyester/cotton blends dyed with a mixture of reactive dyes and disperse dyes. Polymethylol dyes were observed to be suitable for dyeing polyester/cotton blends when used in low concentrations; the required concentrations of polymethylol dyes were only 23–58% of the concentrations of commercial reactive dyes required to reach a given colour level on polyester/cotton blends. The wash and crocking fastness of polyester/cotton blends dyed with polymethylol dyes were similar to those of polyester/cotton blends dyed with reactive dyes.     

Effects of additives on the dyeing of cotton yarn with the aqueous extract of Combretum latifolium Blume stems

Flavonoid constituents from the aqueous extract of the stems of Combretum latifolium Blume sourced in Thailand have potential use as dyestuffs for cotton dyeing. In an effort to improve current natural dyeing methods with this extract, further aspects of the process were studied. It was found that, before equilibrium was reached, an increase in temperature led to an increase in dye adsorption rate of the extract; the initial rate and extent of dye adsorption was further increased by the addition of sodium chloride to the dyebath. In addition, cotton yarn pretreated with a chitosan solution (with and without a crosslinking glyoxal solution), followed by dyeing with C. latifolium extract, provided better depth of shade and also gave better fastness to light and washing than the untreated cotton yarn. Post‐mordanting cotton yarn with a biomordant solution from Memecylon scutellatum leaves also gave good light and wash fastness of the resulting dyed cotton, comparable with the dyeing results with the less environmentally friendly alum as a mordant.     

Metal mordanting in dyeing with natural colourants

Metal mordanting, or the application of metal salts, is a common method of improving the light fastness in dyeing with natural colourants. This review presents the results from a survey of the literature on metal mordanting to assess what levels of correlation exist between mordant‐induced effects (changes in colour and colour depth) and the changes in light fastness, what is known about the mechanisms of mordant‐induced improvements of light fastness, and how the salt levels used in coloration processes compare with the limits on metal levels in wastewater and on the dyed substrates. No strong interrelationships are found between the mordant‐induced effects and light fastness improvements. Knowledge about mechanisms of mordant effect on light fastness appears, in large part, to be derived from empirical correlations. However, as light fastness is affected by a multitude of factors, the correlations do not always hold true. It is found that residual metal contents in spent dye/mordanting liquors are generally not reported. However, with rough calculations, it is estimated that, with even the lowest reported salt concentrations, the metal contents in spent liquors exceed environmental release limits. The metal contents on dyed substrates are also not generally reported, but similar estimations show that the contents of heavy metal on dyed substrates (when copper and chromium salts are used as mordants) also exceed limits. On the basis of these observations, the authors make suggestions for elements to be included in investigations on furthering the use of natural colourants in textile dyeing.