The Release of Disperse Dyes from Thickener Films during Thermal Processes

The dye release properties of hydrophilic polymer layers containing disperse dye particles have been studied. Polymers which form homogeneous films, such as sodium alginate, act as barriers to the passage of dye vapour, unless the weight of the dye particles initially present in the layer exceeds the weight of polymer. Sodium carboxymethyl starch does not behave in this way, as the polymer film is heterogeneous. Evidence is presented for much improved dye release from coatings containing homogeneous film–forming polymers by the emulsification of hydrocarbons into print pastes. The driedcoatings take on a cellular structure which allows disperse dye vapour to be readily released.     

Dye–polymer interaction in nylon 66

Absolute orientation factors of dye and the amorphous region of the polymer nylon 66 have been determined from the dichroism of the visible band and that of the characteristic amorphous infrared band of the polymer. It has been shown that the orientations show a linear relationship with unit slope irrespective of whether the film was stretched before dyeing (prestretched) or stretched after dyeing (poststretched). The relation is the same for reactive as well as nonreactive disperse dye. The effect of thermal treatment at constant length shows that the dichroism of the dye decreases whereas that of the polymer does not and that it is reversible. It is concluded that disperse reactive as well as nonreactive dyes have specific interaction sites with the polymer.     

Exhaust dyeing of polyester‐based textiles using high‐temperature–alkaline conditions

The factors affecting the dyeability of polyester‐based textiles with disperse dyes in an alkaline medium were studied. It was found, for a given set of dyeing conditions, that (a) the appropriate conditions for attaining a higher color yield were 45 min at 130°C with pH 9 using a material‐to‐liquor ratio of 1/10; (b) increasing the Diaserver® AD‐95 concentration to 2% ows (based on weight of substrate) as well as including triethanolamine to 2% ows in the dyeing formulations bring about a significant improvement in the dye uptake; (c) both a preheat setting from 160 to 200°C/30 s and an alkaline weight reduction have a positive impact on postdyeing with the used disperse dye; (d) the extent of dye uptake as well as the color strength are governed by the type of substrate, that is, knitted fabric > spun yarn > woven fabric, nature of the dye stabilizer, that is, EDTA > Diaserver® AD‐95 > Tinoclorite® CBB > citric acid > none, as well as kind of the disperse dye; (e) direct reuse of the disperse dyebaths, without reconstitution, in the dyeing of the used substrates was shown to be feasible in a single shade and in the reverse‐order dyeings (dark → light); (f) one‐bath, one‐step exhaust dyeing of polyester/cotton‐knitted fabric using selected disperse reactive dyes combinations under high‐temperature alkaline conditions is feasible; and (g) the color and fastness properties of the resultant dyeings depend on the type of the used auxiliaries, in addition to the nature of disperse/reactive dyes combinations as well as compatibility with other ingredients. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3563–3573, 2003     

The Behaviour of Disperse Dyes at High Temperatures

Investigations on disperse dyes in the vapour phase are described. The various methods of determining the vapour pressure of such dyes at high temperatures are compared. By means of direct spectrophotometric determination, a relation is established between the partial vapour pressure of a disperse dye over its solution in polyester, and its concentration in polyester. It is shown that the heat-fastness properties of such dyes depend on their vapour pressures, any exceptions being due to the instability of the particular dye under the conditions of testing. Finally, the kinetics of such processes are considered and some attempt is made to analyse practical systems.     

Dyeing behaviour of aqueous solutions of dispersant–free disperse dyes in the high–temperature dyeing of polyester (Part 1)

High–temperature dyeing of polyester with dye dispersions and dispersant–free disperse dyes dissolved in the presence of a surfactants mixture has been simulated with the aid of both a previously developed and a new mathematical model, and the exhaustion kinetics have been computed for three dyes with the aid of experimentally determined dyeing parameters. The correctness of the models was tested by experimentally determined exhaustion curves. An equilibrium in the system consisting of a substrate, dye and surfactant mixture has been investigated experimentally as a function of the temperature and of the concentrations of the dye.     

One-bath dyeing of wool/polyester blends with acid and disperse dyes. Part 2 — disperse dye distribution on polyester and wool

Disperse dye distribution on polyester and wool during one-bath dyeing of wool/polyester blends is discussed. The addition of carriers increases the wool's intrinsic saturation value for disperse dye, thus raising the degree of staining on the wool component at the low dye uptakes. However, staining can be minimised if the dyeing is close to or attains equilibrium conditions. Sequestering agents can accelerate the disperse dye diffusion out of the wool fibre, further reducing staining on wool and transferring more disperse dyes from wool to polyester. Citric acid can be used as a sequestering agent as well as a pH adjusting agent.     

Fungal colorants in applications – focus on Cortinarius species

Secondary metabolites in fungi offer an interesting source of bio‐based compounds that could be used as colorants in many applications. From a historical point of view, fungal natural dyes have been used more rarely than plant‐based dyes. This paper investigates the potential of fungal colorants, using Cortinarius species as examples. In our research, fruiting bodies of the fungi Cortinarius sanguineus and Cortinarius semisanguineus were used as sources of anthraquinone dyestuffs. From 10 kg of fresh fruiting bodies, 60 g of anthraquinone powder was obtained, 6% of the dry weight content. The most abundant compounds were emodin, dermocybin and their glucosides, which formed over 90% of the total dyestuff amount. Pure emodin and dermocybin, as well as the crude water extract, were used for the dyeing and printing of natural and synthetic fibres. Conventional mordant techniques and high‐temperature (HT) disperse dye techniques were applied, and light and washing fastness were tested according to International Organization for Standardization standards. Our experiments show that the yields of dye powders extracted from fungi are reasonable compared with the yields of, for example, madder (Rubia tinctorum). Natural anthraquinones produce strong and bright colours on several types of fibres. In particular, for HT disperse dyed polyester, the light and washing fastness properties were excellent. Anthraquinones are common in nature and there are many fungal species which produce them, so there are a variety of possibilities for growing fungi. The use of large‐scale cultures is an interesting perspective for future biocolorant production.     

Copolyester studies. IV. Dyeing behavior of drawn and undrawn fibers derived from tetramethylene terephthalate–tetramethylene sebacate copolymers

Drawn and undrawn fibers of tetramethylene terephthalate–tetramethylene sebacate copolymers, containing up to 20 mol % of the latter, have been dyed in an infinite dyebath with a disperse dye. The dyeing process has been interpreted in terms of the equilibrium dye absorption, the half-time of dyeing, and the diffusion coefficient. Increasing sebacate content has been found to have a marked effect on the rate and level of dye uptake. Deviations from Fickian behavior have been observed for the drawn fiber and related to presence of voids.     

Dyeing behaviour of aqueous solutions of dispersant–free disperse dyes in the high–temperature dyeing of polyester (Part 2)

High–temperature dyeing of polyester with true solutions of crude dyes and dispersant–free disperse dyes dissolved in the presence of a surfactant mixture has been simulated with the help of two mathematical models. The dyeing behaviour, i. e. the kinetics of exhaustion and of dye distribution in the fibre have been evaluated for nine hypothetical dyes. In the first method kinetics of hypothetical crystalline modifications of three Terasil dyes and in the second method for hypothetical surfactants have been studied. For both methods the laws governing the dyeing behaviour have been formulated. The advantages and disadvantages of the methods and the scope for implementing them are discussed.     

Scientific Aspects of Transfer Printing

The mechanism of vapour phase transfer printing is described on the basis that the process involves a 3-phase system consisting of a printed dye layer separated from a fabric by air space. The behaviour of dye in each phase under transfer printing conditions is examined and recent experimental results on differential air flow and permeability of printed paper are described. Finally the development of disperse and other dye structures for specific use in transfer printing is reviewed.     

The dyeing of nylon with a microencapsulated disperse dye

Melamine resin microcapsules containing CI Disperse Blue 56 were prepared by in situ polymerisation. The microcapsules were characterised by their thermal properties and morphology, such as particle size and particle size distribution. The dyeing behaviour of the microcapsules on nylon 6.6 was evaluated. The microencapsulated dye exhibited good build-up, levelness and fastness properties. It has been demonstrated that microencapsulated disperse dye can be used to replace commercial disperse dyes in dyeing polyamide fabric without dyeing additives, and the resulting effluent can be easily recycled after filtration.     

Structure–property relationships for azo disperse dyes on polyurethane fibre

Using two series of monoazo disperse dyes, the relationships between the molecular structure of dye and its dyeing properties, such as adsorption behaviour, fastness properties and distribution on polyurethane–polyester blends, were thoroughly investigated. Correlation analysis of experiment data revealed that the partition coefficient between octanol and water (CLogP) is the main factor affecting dye sorption. A greater level of CLogP tends to have a greater isotherm coefficient and better rubbing and washing fastness on polyurethane fibre, as well as a greater distribution ratio between the components of the blend. The dye dipole moment is negatively correlated with various degrees of washing fastness. The dye with two terminal hydroxy groups exhibited notable sorption on the polyurethane component and has the largest partition ratio on polyurethane–polyester in the blend. Corresponding regression analysis equations were identified.     

Effects of Gaseous Diffusion in the Substrate on Light Fastness of Dyes

Various disperse dyes in cellulose triacetate (cta) film and some dyes in Cellophane regenerated-cellulose film, sealed in envelopes of undyed hydrophobic films, viz. polytetrafluoroethylene (ptfe), polyacrylonitrile (pan), polyethylene terephthalate) (pet) and cta, have been exposed to light from a 400-W mercury lamp. Fading is retarded by the undyed films. The order of effectiveness is ptfe> pan > pet > cta. The permeability of water vapour (except for pan) or oxygen through these films decreases in the above order. The retardation is similar in magnitude to the corresponding differences in light fastness of the disperse dyes on textile fibres. It is suggested that the action, except possibly in pan, is caused by retardation of the diffusion of an oxygen molecule towards contact with a dye molecule during the short life-time of the excited state of the dye; calculation shows that there is only a very small chance of such contact. An expression is derived which shows that the rate of fading depends on both the life-time of the excited dye molecule and the rate of diffusion of oxygen in the substrate. The retardation effect, termed ‘diffusion-restriction’ (dr) effect, probably operates to some extent in all fading of colorants in fibres or films.     

Yttria–polystyrene–polypropylene composite for fine dyeable fibers

Fine polypropylene fiber has many excellent properties, but it is difficult to dye because of the absence of dye sites in the molecular chain and high crystallinity. Fine polypropylene/hybrid polystyrene (yttria) fiber melt‐spun from blends of polypropylene and a small amount of nanohybrid polystyrene with modified yttria incorporated was prepared to improve the dyeing properties. The dyeability, orientation, degree of crystallinity, phase morphology, and mechanical properties of pure polypropylene and the blend fibers were investigated. It was found that the crystallinity and morphology of these phases in the blend systems were different. With the existence of nanohybrid polystyrene, the fine modified polypropylene filaments had practical mechanical properties, the amorphous region of the polypropylene/hybrid polystyrene (yttria) fiber increased, and the modified polypropylene fiber dyed easily and had good fastness to soaping because of the complexation of the disperse dye and yttrium in the blend system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effect of heat setting on the dyeability of differentially dyeable polyester fibres

Apparent diffusion coefficients of two disperse dyes for so-called easily dyeable/cationic-dyeable polyester (ED-CDPET) and cationic-dyeable polyester (CDPET) fibres of identical linear density and sulphonic acid group content have been calculated. It was found that the diffusion coefficients of dyes for ED-CDPET were far greater than those of dyes for CDPET. The dyeability at the boil without carrier, using disperse and cationic dyes on various ED-CDPET and CDPET fibres, has been studied. ED-CDPET was found to have higher dyeability at all levels of heat setting (irrespective of the dye used). The finest ED-CDPET fibres showed maximum dye uptake as a result of increased surface area. Heat setting in the taut condition reduced dye uptake.     

Dye demand/supply ratio as a predictor for the unlevelness of disperse‐dyed polyester

The ratio of the demand for dye by the fibre and the supply of dye by the dyebath is a useful indicator to predict unlevelness in the exhaust dyeing of polyester with disperse dyes, provided that dispersion breakage is small. The ratio can be calculated from the dye exhaustion curve, the dye solubility and the flow rate in the machine. The findings suggest that unlevelness can be successfully controlled by ensuring that dye demand never exceeds dye supply at any moment during the dyeing process.     

Non–destructive near–infra–red analysis for the identification of dyes on textiles

A pattern–recognition algorithm combined with near–infra–red reflectance spectroscopy has been modified to function as a non–destructive analysis technique for identifying dyes present on textiles. Samples of 261 dyes and textiles were measured in the 1100–2500 nm region to form a near–infrared (reflectance) spectral library. Principal component analysis (PCA) was used to generate an orthonormal reference library from the library of original spectra. The PCA algorithm treats the spectra in the library as an n component quantitative analysis problem in which each spectrum represents a standard mixture having a concentration of 1. 0 for that component. Spectra of dyed textiles were used as an unknown set in a library search. This new method saves time and materials in comparison with traditional methods of analysing dyes present on textile fibres. The library of dye spectra can be developed from measurements made directly on dye powder without interference from inorganic diluents. The method was successfully used to identify the dyes present on five textiles. The technique is particularly well suited for studying forensic, historic and archaeological textiles because of its non–destructive nature and ability to analyse small amounts of sample.     

The roles of elevated temperature and carriers in the dyeing of polyester fibres using disperse dyes: Part 1 fundamental aspects

This review concerns the application of disperse dyes to poly(ethylene terephthalate) (PET) fibres using aqueous immersion dyeing processes and the roles of both elevated dyeing temperatures and carriers in such dyeing systems. This part of the paper presents a review of the fundamental properties and characteristics of PET fibres, disperse dyes and dyeing accelerants. In the next part of the paper, the various theories and concepts that have been proposed to explain the promotional effects imparted by elevated dyeing temperatures and carriers to disperse dye uptake on PET and other types of fibre, are reviewed and analysed, from the viewpoints of the essential physico-chemical aspects of both the aqueous disperse dye/PET and disperse dye/carrier/PET systems. Later parts of the paper will present a mechanistic model of the disperse dye adsorption process based on dye solubility as well as a novel plasticisation model of dye diffusion.     

Dyeing studies with hydroxyanthraquinones extracted from Indian madder. Part 1: Dyeing of nylon with purpurin†

Purpurin (1,2,4‐trihydroxyanthraquinone) is the major colorant present in the roots of Indian madder (Rubia cordifolia). Its structure is similar to that of disperse dyes. To gain an understanding of the dyefibre interactions involved, kinetic and thermodynamic studies have been conducted with purpurin on nylon fibre. Dyeing corresponds to the Nernst isotherm as linear isotherms were obtained. The dye is found to be sensitive to pH and high temperature. The rate of dye uptake, diffusion coefficient, standard affinity, heat of dyeing and entropy have been calculated and discussed.