Enzymes as auxiliary agents in wool dyeing

The action of three enzymes has been comparatively studied when used as auxiliary agents in dyebath. The absorption rate of the dye, the colour differences between wool dyed with and without enzymes and the colour fastness were determined. The action of enzymes consists of increasing dye absorption and also seems to produce a better diffusion of the dye into the fibre. The use of the enzymes in wool dyeing offers the possibility of dyeing under mild temperature conditions.     

The effect of reactive dyes on damage in wool dyeing

This paper demonstrates that reactive dyes exert a significant fibre–protective effect when dyeing wool fabric; this effect may be measured, in a reproducible manner, using the wet–burst strength test. The effect of dyebath pH, dye concentration, dyebath temperature and dyeing time on wool can thus be evaluated. The magnitude of the above protective effect has been compared with that achieved using commercially available fibre–protective agents. It is concluded that reactive dyes are significantly more effective than the latter agents when employed in medium to full depths. It is proposed that the unusual protective effect afforded by reactive dyes is related to the following factors. Reactive dyes readily react with sulphur nucleophiles, thus inhibiting thiol–disulphide interchange reactions and thereby significantly interfering with the level of set produced in a boiling dyebath. Reactive dyes react preferentially with non–keratinous proteins in the intercellular cement and the endocuticle thus reducing their tendency to hydrolyse and to partially dissolve in the hot aqueous dyebath.     

Improved reactive dyeing of wool with novel trifunctional reactive dyes†

The synthesis of a new trifunctional reactive dye is described in this paper by reaction of a di‐chloro‐s‐triazine dye with the specially synthesised amine, N,N’‐bis{2[(2‐chloroethyl)sulphonyl]ethyl}amine. When applied to wool from boiling dyebaths at pH 5, fixation efficiency values of 96% were recorded even at heavy depths (3% owf). In the case of the β‐chloroethyl sulphone group, there is good evidence that elimination to vinyl sulphone occurs readily in mildly acidic dyebaths at the boil. Since elimination is gradual, the reactive species does not form rapidly allowing migration and level dyeing to be achieved.     

Investigation into the dyeing of wool with Lanasol and Remazol reactive dyes in seawater

Freshwater is an increasingly scarce resource that is extensively used in textile wet‐processing. In seeking to identify alternative low freshwater‐usage coloration technology, this study examined the potential use of seawater (SEAW) as the dyeing medium for wool coloration using a range of reactive dyes. Initially, the dyeing behaviour of the wool fabric in simulated seawater (SSW) was compared with conventional dyeing from distilled water (DW) using α‐bromoacrylamide‐based Lanasol dyes and sulphatoethyl sulphone‐based Remazol dyes. These preliminary studies demonstrated that comparable coloration could be achieved in the SSW medium based on an assessment of the dye exhaustion, dye fixation, colour yield and levelness. Subsequent dyeing studies of wool using Mauritian seawater with both the Lanasol and Remazol reactive dyes confirmed that, based on the dye exhaustion, dye fixation, colour yield and levelness, comparable coloration could be achieved, highlighting the possibility of substituting freshwater with seawater as the dyeing medium.     

Reactive dyeing systems for wool fibres based on hetero-bifunctional reactive dyes. Part 2: Investigation of dyeing properties during the dyeing cycle

The dyeing behaviour during the dyeing cycle of a Sumifix Supra dye and some other commercial reactive dyes under various dyebath pH conditions was investigated. Studies of the dyeing of wool serge fabric indicated that the diffusion properties of hetero-bifunctional Sumifix Supra dyes generally lie between those of b-sulphatoethylsulphone (Remazol dyes) and monochlorotriazine (Procion H dyes).     

One-bath dyeing of wool/acrylic blends with reactive cationic dyes based on monofluorotriazine

A series of reactive cationic dyes containing the monofluorotriazine structure has been synthesised and their dyeing behaviour on wool, acrylic and a 50:50 wool/acrylic blend studied using a one-bath method. The results indicate that reactive cationic dyes having this structure give a high level of exhaustion and fixation on these fibres. Fastness properties on the wool/acrylic blend were also in general very good.     

Retardation of the photoyellowing of untreated wool and wool treated with fluorescent whitening agents by the action of reducing agents

Different chemically treated wools have been exposed to radiation in the presence of different aqueous reductive bleaching agent solutions. It was observed that thiourea dioxide gave the best performance and, in the case of wool serge, led to a fabric having a better light fastness. An interesting beneficial synergistic effect was uncovered when the reducing agents were used in conjunction with formaldehyde. Biphenols (models for dityrosine) have also been padded onto wool and exposed to light in the wet state to mimic the photoyellowing of dityrosine. 0, 0′-Biphenol-treated wool was exposed to light in the presence of the reducing agents and these were found to decrease the amount of discoloration produced by degradation of 0, 0′-biphenol.     

Application of chitosan/nonionic surfactant mixture in reactive dyes for dyeing wool fabrics

The feasibility of wool fabrics pretreated with a chitosan/nonionic surfactant mixture and dyed with reactive dyes was studied. The results showed that the presence of the chitosan/surfactant improved the application to wool, which greatly enhanced the color strength when dyed at 50°C but little change was observed when dyed at 80°C. The higher the concentration of chitosan/surfactant added, the greater was the color strength of the dyed wool fabrics. The amounts found to be optimum for dyeing were 0.5% chitosan and 1.0% surfactant. The washing fastness of the dyed wool fabrics was in the range of grades 4–5, the dry rubbing fastness was in the range of grades 4–5, and the wet rubbing fastness was in the range of grades 3–4. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2859–2864, 2001     

Non-isothermal dyeing of wool

Kinetic models of the dyeing process are reviewed and diffusion of dye into the fibre is identified as the rate-determining step in most dyeing processes. A simpler approach to defining a linear exhaustion profile of acid dyes on wool fibres is proposed that takes into account non-isothermal kinetic models and analyses their possibilities of use. In this endeavour a novel dyeing rate constant is defined that appears to be characteristic of a particular dye class.     

Reactive dyeing systems for wool fibres based on hetero-bifunctional reactive dyes. Part 1: Application of commercial reactive dyes

The wool dyeing properties, such as exhaustion and fixation parameters, of selected hetero-bifunctional Sumifix Supra dyes and some other commercial reactive dyes were quantified under various dyebath pH conditions. Studies of the dyeing of wool serge fabric indicated that Sumifix Supra dyes could produce reasonably high fixation values. However, remarkably improved fixation values were obtained when these dyes were pre-activated to the vinylsulphone form and dyed in this form, especially at low pH values (pH 4 or lower).     

The efficiency of reaction between reactive fluorescent whitening agents and wool

Potential fluorescent whitening agents (FWAs) containing halogen atoms which intramolecularly quench fluorescence have been synthesised and applied to wool in a number of ways. Application by cold pad-batch methods revealed that the complete displacement of all halogen atoms by nucleophilic groups in wool did not take place. Treatment of these materials with morpholine, sodium carbonate or water was necessary to develop the full potential fluorescence yield of the FWA on the fabric. The fluorescence of FWAs can be quenched by the heavy atom effect, as shown by the fact that no fluorescence was observed when commercial FWAs were applied to brominated wool. If the FWA-treated brominated fabrics were subjected to a reduction treatment then the bromine atoms were removed and the fluorescence of the FWA was restored. Application of the potential FWAs by exhaustion, with thioureadioxide present in the liquor, at high temperatures always led to strongly fluorescent fabrics, implying that the halogen atoms were completely displaced using this application method, but the question remains as to how much of the displacement leads to covalent bonds between the fabric and the FWA.     

The effects of residual surfactants on the dyeing of wool

Wool fabric was extracted with various organic solvents at their boiling points and then dyed with Coomassie Blue BL200. Non–dyed areas of fabric were observed after extraction with ethanol, acetone/ water (70:30) and chloroform/methanol (70:30) mixtures, but not after extraction with perchloroethylene. Silica column chromatography separated the extracts from various solvent pretreatments into five major peaks, based on mass obtained. Some of these peaks were shown to contain cholesterol, non–ionic surfactant and phospholipid. Up to 14 components were detected by two–dimensional thin layer chromatography of the extracts. Thin layer chromatography revealed that some of the more polar components were not extracted by perchloroethylene. Separation of the extracts by column chromatography enabled a study of dye uptake to be carried out after recontamination of pretreated fabric with the major fractions. Materials in two of these fractions were found to eliminate the uneven dyeing observed with Coomassie Blue BL200. Column chromatography and spot tests showed that they behaved similarly to the non–ionic surfactant Antarox CO 630. These experiments also showed that refluxing perchloroethylene extracted only about half as much non–ionic surfactant as did refluxing chloroform/methanol (70:30) mixture. The residual surfactant may originate from the scouring process and/or from processing oils such as Mulrex.     

Acid dyeing isotherms of cotton fabrics pretreated with mixtures of reactive cationic agents

Reactive cationic agents, phenylmonochlorotriazinyl and epoxypropyl, are used for cotton pretreatment using a pad–dry–curing technique. The dyeability of cationised cotton fabrics using CI Acid Red 1, determined spectrophotometrically for the residual dyebath, has been dependent on the cationic agent concentration and the appropriate mixture used. Comparative sorption isotherms, rate of dyeing at different temperatures, standard affinity, entropy and heat of dyeing for three different pretreated fabrics have been calculated and discussed. The equilibrium data obtained were fitted by the Langmuir isotherm model, allowing the corresponding sorption parameters to be determined.     

Plasma modification on wool fibre: effect on the dyeing properties

The dyeing properties of wool fibre treated with low-temperature plasma (LTP) were investigated kinetically and thermodynamically. Three non-polymerising gases, namely oxygen, nitrogen and a 25% hydrogen/75% nitrogen gas mixture, were used for the LTP treatment. It was found that the dyeing rate, dye uptake, standard affinity, heat of dyeing, entropy of dyeing and activation energy of diffusion were improved after the treatment.     

Application of a chitosan/nonionic surfactant mixture to wool assessed by dyeing with a reactive dye

Chitosan application to wool is known to be associated with problems such as its weak binding and uneven distribution. In an attempt to overcome such problems, chitosan was applied from a mixture with a nonionic surfactant. A weak time interaction was observed between chitosan and the surfactant over time, resulting in changes in the conformation of chitosan in solution, which was confirmed by viscosity measurements. The presence of chitosan/surfactant association improved the application to wool, which was assessed by dyeing the treated wool with a reactive dye at 60°C. Since this technique offers the possibility of producing deeper and more vivid colours without increasing the concentration of dye used, dyeing was also carried out at 95°C, closer to practical dyeing conditions. An improvement in the fixation of the reactive dye was observed.     

The effect of liposome on dyeing mohair/wool blends

The aim of this study was to examine the use of liposome in the dyeing of wool and mohair fibres with acid dyestuffs. Soybean lecithin and cholesterol were used to form the liposome membrane utilised in the dyebath. Liposome production was performed according to the thin lipid layer method (Bangham Method) using a rotary evaporator. Two different forms of liposome were used for dyeing wool and mohair fibres. In its first form, liposome was utilised as an auxiliary agent, where it was added to a conventional dyebath at the beginning of the process. In its second form, dyes were encapsulated with liposome and then used in dyeing. The effects of these two different forms of liposome were compared with conventional dyeing. Dyeing was carried out at depths of shade of 0.5%, 1.0% and 2.0% using three different concentrations of liposome (0.33%, 0.66% and 1.33%). An analysis of K/S values, fastness to washing, and the alkali solubility of fibres was conducted. The fibre samples dyed in the presence of liposome exhibited very good fastness to light (grade 8). The wash fastness test results of the liposomal‐dyed samples were significantly better (grade 4‐5) than for those samples which were conventionally dyed. In the presence of liposome, the tensile strength of fibres was 20 gf, whereas it was 11 gf without liposomes.     

Absorption of betaines by wool and its effect on dyeing

This paper reports a study of betaine absorption by wool, the main parameters affecting it and its influence on dyeing with acid dyes. An attempt to establish the types of interaction between fibre, betaine and dye is discussed. The influence of pretreatment with various betaines on the dye distribution (whether the dye is superficially deposited or has diffused into the fibre) throughout the whole dyeing process is also studied.     

One‐bath union dyeing of a modified wool/acrylic blend with acid and reactive dyes

Pretreated wool/acrylic fibre was obtained by a facile amidoximation process. Fibre characterisation (nitrogen content, tensile strength, shrinkage, infrared spectra and X‐ray diffraction) proved the success of the pretreatment. Union dyeing of wool/acrylic fabrics with acid and reactive dyes, namely CI Acid Red 40, CI Acid Blue 25, CI Reactive Red 194 and CI Reactive Blue 25, was obtained using a one‐bath dyeing process. Different factors that may affect the dyeability of the blend fibre, such as dyebath pH, liquor ratio, temperature, time and dye concentration, were evaluated with respect to the dye exhaustion, fixation, colour strength, levelling and fastness properties. Excellent to good fastness was obtained for all samples, irrespective of the dye used. The result of the investigation offers a new viable method for union dyeing of wool/acrylic fibres in a one‐dyebath process.