The Ef]fect of a Synthetic Tanning Agent on the uptake of Acid Dyes by Nylon 6

The effect of pretreating various nylon 6 fibres with a synthetic tanning agent on the rates of dyeing of five acid dyes has been studied. From the adsorption properties of these dyes on nylon 6 samples differing in amine end-group content, it is shown that as the basicity of the dye increases, the saturation value tends to approach more closely to the content of amine end-groups in the fibre. For a monobasic, hydrophobic dye, the saturation value is not governed by the amine end-group content of the fibre. Assuming that an increase in hydrophobicity results in a higher dye anion affinity, it is suggested that as the affinity of the dye for the fibre increases, the rate of dyeing becomes less affected by the presence of the synthetic tanning agent. For dyes of low affinity and greater hydrophilic character, the rate of dyeing of pretreated nylon is initially low but increases as the dyeing proceeds. It is postulated that this is caused by the initial deposition of the syntan in the outer regions of the fibre acting as a partial barrier to dye diffusion. Although the syntan does not desorb significantly during dyeing, it diffuses slowly into the fibre and gradually loses some of its retarding influence.     

The Determination of Diffusion Coefficients as a Function of Concentration for Dyes in Fibres

A method of determining the dependence on dye concentration of the diffusion coefficient of dyes in fibrous substrates has been developed, based on an approximation method of Crank, in which the amount of dye adsorbed by the fibre is measured colorimetrically as a function of time. The method has been applied to two dyeing systems, the direct dye Chlorazol Sky Blue FF (C. I. Direct Blue 1) on rayon and the acid dye Naphthalene Scarlet 4R (C. I. Acid Red 18) on nylon 6. 6. The results are in good agreement with those of R. H. Peters et al. for the same dyes and substrates, although Peters used films and not fibres and determined diffusion coefficients by an experimentally more complex method that appears impractical for fibres, the film being sectioned and the dye concentration measured as a function of distance with a microdensitometer.     

Ultrasonic‐assisted dyeing: II. Nylon fibre structure and comparative dyeing rate with reactive dyes

Comparative dyeing kinetics of nylon‐6 fibre with different reactive dyes using conventional and ultrasonic conditions are presented. The time/dye‐uptake isotherms are revealing the enhanced dye‐uptake in the second phase of dyeing (diffusion phase). The data of dyeing rate fit well with the integrated form of the first‐order rate equation and values of dyeing rate constant and half‐time of dyeing are discussed. Ultrasonic efficiency in accelerating the dyeing rate relative to conventional heating was examined for all dyes used to show that ultrasonics are most effective for a dyeing system which has difficulty in achieving high dye‐uptake. To clarify the role of fibre fine structure and whether it is affected during dyeing with ultrasonic waves, time‐dependent ultrasonic pre‐treatment of nylon‐6 fibres and its effect on the colour strength obtained is presented. X‐ray diffraction studies on nylon‐6 fibres conventionally and ultrasonically pre‐treated have shown that the percentage of fibre crystallinity has become higher in ultrasonically treated fibre in comparison with that of conventionally treated. Although the increased crystallinity of the fibre, which occurs simultaneously during the ultrasonic dyeing process, would retard dye uptake, it seems that the enhanced effect of power ultrasonic is high enough to overcome this side‐effect on the fibre. © 2003 Society of Chemical Industry     

The influence of polymer and dye characteristics on diffusion in nylon 66

A study has been carried out of the relationship between polymer orientation and dyeing behavior using a specially prepared range of nylon 66 samples varying only in orientation and five dyes normally showing varying degrees of sensitivity to physical variations in nylon. Integral diffusion coefficients have been calculated using Crank's finite dyebath equation from appropriate rate of dyeing data. Evidence has been produced which suggests that except with dyes of low molecular weight, i.e., dyes insensitive to physical variations in the nylon, a diffusional interaction between diffusing dye molecules exists which leads to a variation in the concentration dependence of the diffusion coefficient with fiber orientation. The length of the diffusing dye ion has been shown to be of decisive importance in this interaction.     

Transport of acid dye in nylon and concentration dependence of the diffusion coefficient

The dyeing kinetics of an acid dye (C. I. Acid Blue 40) in a nylon 6 film were investigated using partition-cell and film-roll methods at 80°C and pHs 2.3 and 3.05. The concentration dependence of diffusion coefficient of the dye in the nylon substrate measured by both methods was interpreted in terms of parallel diffusion with biomodel sorption of the Nernst and Langmuir modes. As the concentration of dye increases, the transport of dye inside the nylon film becomes dominated by pore diffusion and surface diffusion of sorbed Nernst populations.     

Dyeing properties of oxygen low-temperature plasma-treated wool and nylon 6 fibres with acid and basic dyes

Wool and nylon 6 fibres treated with oxygen low-temperature plasma were dyed with acid and basic dyes. Despite the increase of electronegativity of the fibre surface caused by the plasma treatment, the rate of dyeing of wool was increased with both dyes, while that of nylon 6 was decreased with the acid dye and increased with the basic dye.     

Determination of Acid-dye Standard Affinities for Nylon Fibres from Sorption Isotherms

The dyeing equilibria of acid dyes on nylon 6.6 are studied using a model in which the substrate is divided into solid polymer and an internal solution. A Nernst distribution is assumed for the distribution of dye between these two phases, while a Donnan equilibrium is presupposed for that between the internal and external solutions. It is shown experimentally that the Donnan coefficient of the nylon increases exponentially with the amount of fixed dye provided that the substrate is initially present in the isoelectric state. Based on this finding, the standard affinity of an acid dye for nylon 6.6 can be derived from the sorption isotherm, without the necessity of knowing the acidity and basicity of the carboxyl and amino groups respectively. The effect of introducing an alkyl group on the standard affinity is demonstrated with four anthraquinone dyes.     

2-Pyrazoline Dyes for Wool and Nylon

A range of yellow fluorescent 2-pyrazoline acid dyes has been synthesized. Their spectral and dyeing properties (on wool and nylon) depend both on the nature of the substitution pattern of the dye and on the nature of the fibre substrate. Exhaustion and fastness to washing, which are better on nylon than on wool, are improved by substituents attached to the 2-pyrazoline ring. Fastness to light is independent of the fibre and is increased by substituents on the 4- and 5- positions of the 2-pyrazoline ring. The fastness properties of the pyrazoline dyes were compared with those of C.I. Acid Yellow 7.     

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.     

Developments in Coloration for the Carpet Industry

Meeting of the Bradford Junior Section, held in Bradford Technical College, on 13 October 1969, Mr R. S. Stringer in the chair The improvement in wet fastness of anionic dyes, e.g. C.I. Acid Blue 25, on nylon fibres by aftertreatment with natural tannins is attributable mainly to modification of the substrate by the tannin, which lowers the rates of diffusion of the dye (a) out of the dyed fibre and (b) into undyed adjacent nylon. Ultraviolet spectroscopy of solutions of tannic acid (a polygalloylated glucose) has given indications of the alkaline oxidative degradation of the tannin believed to be responsible for the discoloration of backtanned dyeings. Tartar emetic increases the effectiveness of backtanning by formation of a less soluble complex with tannic acid which is more resistant to alkaline oxidation. Formic acid increases the rate of diffusion and the equilibrium uptake of tannic acid on nylon. The adsorption and diffusion behaviour of several related anthraquinone acid and disperse dyes on nylon is discussed and possible explanations are advanced of the low effectiveness of backtanning in preventing loss of dye by dyed nylon 6 and staining of undyed wool. No conclusive evidence has been obtained of interaction between C.I. Acid Blue 25 and tannic acid or tartar emetic in aqueous solution.     

Reaction and diffusion of reactive disperse dye in nylon 6

The diffusion of a reactive disperse dye with a vinylsulfonyl group accompanied by simultaneous reaction with the amino end groups in nylon 6 was examined by the method of cylindrical film roll at 70°C and pH 2.2–8.0. The experimental diffusion profiles of the active and fixed species of the dye in nylon 6 were confirmed to be described by the diffusion equation accompanied by the chemical reaction with substrate taking the limited amount of the end groups into account, where the active species of dye were assumed to react only with the free base of amino end groups. The completion of the reaction with the amino end groups was observed in the first layer from the surface at pH 6.0–8.0. The value of diffusion coefficient was constant (8.0 × 10^?10 cm²/s) at all the pH's. The product of the second-order rate constant, k₂, of reaction of the dye and the dissociation constant, K_a, of the amino end groups was constant (k₂K_a = 4.0 × 10^?9 s^?1) at pH 2.2–8.0. The k₂ values of the reaction with various substrates for vinylsulfonyl and monochlorotriazinyl-reactive dyes were compared and the practical dyeing conditions were discussed.     

The roles of polymer relaxation phenomena,aqueous dye solubility and the physical properties of water in the mechanism of adsorption of a disperse dye on poly(ethylene terephthalate) fibres: part 5 analysis of polymer relaxation phenomena for different polymers

The temperature dependent uptake of a commercial disperse dye on cotton and polyamide 66 fabrics at dyeing temperatures between 30°C and 130°C adhered to the Williams–Landel–Ferry equation, insofar as, very good correspondence was observed between plots of experimentally determined colour strength data points (log1/f_k) and the respective structural relaxation times of the cellulose and nylon 66 polymers (loga_T data points), as a function of the parameter (T − T_g). Adsorption of the dye on both types of fibre therefore concurs with the fundamental precept of the free volume model of dye diffusion. Comparison of the adherence of the uptake of the commercial dye on cotton and polyamide 66 fabrics with that secured on polyester fabric revealed that despite the major chemical and physical differences between the three types of fibre, the same dyeing mechanism likely applies to each fibre type. The marked temperature dependent uptake of the commercial grade disperse dye each of the three types of substrate is the consequence of two, different, but inherently interconnected, thermally activated phenomena, namely the relaxation times of the molecular rearrangements occurring within the respective cellulose, nylon 66 or poly(ethylene terephthalate) macromolecule, in which polymer glass transition assumes the principal role, and the aqueous solubility of the commercial grade disperse dye.     

Ultrasonic‐assisted dyeing: I. Nylon dyeability with reactive dyes

The use of ultrasonic power (38.5 KHz, 350 W) to assist the dyeability of nylon‐6 fibre with reactive dyes is reported. The effects of the different factors that may affect the dyeability of nylon‐6 fibre with Reactive Red 55 were simultaneously carried out under both ultrasonic power and conventional heating conditions. The colour strength values obtained for the dyed samples using ultrasonic power were higher than those obtained using conventional heating. Also, the effect of alkaline soaping treatment on dye fixation for the dyed fabrics with different reactive dyes, at both acidic and neutral pHs, is generally better with ultrasonic than with conventional heating. The overall results indicate that the enhancing effect is mainly attributed to the de‐aggregation of dye molecules, which leads to better dye diffusion and possible assistance for dye‐fibre covalent‐bond fixation. The results of wet fastness properties of the dyed fabrics reveal improvement using ultrasonic power dyeing relative to the conventional heating method. © 2003 Society of Chemical Industry     

Dyeing Kinetics of an Acid Dye in a Nylon Film

The dyeing kinetics of an acid dye (C. I. Acid Blue 182) in a nylon 6 substrate was investigated using partition–cell and film–roil methods. The concentration dependence of the diffusion coefficient of acid dye in the nylon film was derived from both methods and compared with a prediction based on diffusion together with adsorption equilibrium established instantaneously between mobile and immobilised dye molecules in pores. These two sets of experimental results were found to be incompatible with each other. It was deduced that two kinds of region exist in the nylon, one being a region available for rapid penetration and the other, connected to it and formed by slow relaxation, a region of poor penetration.     

Diffusion of disperse dyes into super-microfibres

The disperse dyeing process for polyester fibres is complex. It is characterised by the diffusion-controlled sorption of dyes and depends on dye concentration, dyebath temperature, dye liquor flow rate and fibre count. Moreover, the dyeing properties of super-microfibres are also quite different from those of microfibres or conventional polyester fibres. In this paper the influence of dyebath temperature, initial dye concentration and fibre count on the diffusion coefficient and the sorption isotherms has been studied. The analysis of kinetic properties has been restricted to infinite dyebath conditions. All experimental results have been compared terms of fibre count and dyebath temperature.     

Dye Diffusion-The Key to Efficient Coloration

This paper was presented to the Manchester Region on 14 December 1978, and to the West Riding Region on 22 February 1979.More than any other factor, the rate and degree of diffusion of dyes into the individual fibres composing any textile substrate control the productivity, reproducibility and the quality (with respect to appearance and sometimes the fastness properties) attained in each process. Using direct (fibre cross–section) measurement of the degree of penetration of dyes into nylon, polyester and acrylic fibres, under a variety of application conditions, the relationships between dye penetration and visual colour yield has been determined with fibres differing in cross–sectional shape and delustrant content. The present interest in saving energy, time and water has led to numerous processes resulting in ‘ring–dyeing’. Batchwise dyeing for relatively short times or at somewhat abnormal temperatures, and continuous dyeing by rapid steam–fixation techniques are examples which have been investigated to define application conditions that might be expected to cause problems in bulk–scale production.     

Effect of metal salts on the dyeing of freshly spun polyacrylonitrile fibre with acid dyes

Conclusions The effect of the metal cations Al³⁺, Zn²⁺, and Cr³⁺ on the process of dyeing freshly spun PAN fibres with acid dyes has been studied. It has been found that the greatest amount of dye is fixed on the fibre when Al³⁺ ions are introduced into the dye bath.On the basis of analysis of the IR spectra of the dyed fibres, a mechanism has been proposed for the interaction of both the metal cations and also of the dye with PAN fibre. It has been found that the metal cation is bonded with the fibre both by an ionic bond with the—COOH groups and also by a coordination bond with >C=0 groups of the polymer substrate.Translated from Khimicheskie Volokna, No. 6, pp. 13–14, November–December, 1986.     

Model Calculations on Levelness in Package Dyeing

A simple mathematical model that includes (a) uniform liquor flow through a package and (b) Fickian diffusion of a dye within the fibres is described. The distribution of a dye within the package and the degree of levelness are calculated for constant dyeing conditions (e. g., constant temperature) and a dye with a linear sorption isotherm. The effect on levelness of the dyeing time, rate of liquor flow, liquor–to–goods ratio, package data, diffusion coefficient and final dyebath exhaustion are discussed. Using certain assumptions the levelling time is determined by two parameters only: a diffusion velocity v_D and a streaming parameter s.     

Effect of microencapsulation on dyeing behaviors of disperse dyes without auxiliary solubilization

Microencapsulated disperse dye can be used to dye hydrophobic fabric in the absence of auxiliaries and without reduction clearing. However, little available information for dyeing practice is provided with respect to the effect of microencapsulation on the dyeing behaviors of disperse dyes. In this research, disperse dyes were microencapsulated under different conditions. The dyeing behaviors and dyeing kinetic parameters of microencapsulated disperse dye on PET fiber, e.g., dyeing curves, build up properties, equilibrium adsorption capacity C_∞, dyeing rate constant K, half dyeing time t_1/2, and diffusion coefficient D were investigated without auxiliary solubilization and compared with those of commercial disperse dyes with auxiliary solubilization. The results show that the dyeing behaviors of disperse dye are influenced greatly by microencapsulation. The diffusion of disperse dyes from microcapsule onto fibers can be adjusted by the reactivity of shell materials and mass ratios of core to shell. The disparity of diffusibility between two disperse dyes can be reduced by microencapsulation. In addition, the microencapsulation improves the utilization of disperse dyes due to no auxiliary solubilization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dyeing of Nylon Fabrics with an Acid Dye in a Rotating-disc Contactor

The kinetics of dyeing a nylon fabric with an acid dye (C. I. Acid Blue 182) were investigated using a rotating-disc contactor, and were analysed in terms of intrapolymer diffusion with trimodal (one Nernst-type and two Langmuir-types) adsorption. The resistance of mass transfer from liquor to film in film dyeing was found to be negligible relative to resistance inside the film. The effective interfilament diffusion coefficient in the fabric was found to be dependent on the rotational speed of the disc. It appears that the process of dyeing nylon fabric with an acid dye might be governed by interfilament diffusion of dye in the fabric rather than mass transfer from liquor to fabric and intrafilament diffusion.