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.     

Adsorption thermodynamics and diffusion of disperse anthraquinone dyes in acetate fibre

Diffusion coefficients, thermodynamic parameters and adsorption equilibrium isotherms of some anthraquinone dyes for acetate fibre are reported. The chemical constitution seems to be more important than the size factor in determining dye diffusion into the interior of the fibres. The activation energies of diffusion decreased strongly when o-dichlorobenzene was present, due to the plasticising effect of carrier. Nernst partition isotherms were obtained, up to saturation. Substantivity decreased when water-solubilising groups are present in the molecule.The aqueous solubilities and heats of solution have been measured; the higher ΔH_w values were found for the derivatives which can form intermolecular hydrogen bonding in the crystalline state.     

Carrier dyeing of polyphenylene sulphide fabric with disperse dye

Polyphenylene sulphide is considered to be a high‐performance thermoplastic material and has been used in many areas over the past few decades. But the application of polyphenylene sulphide fabric used for protective clothing is limited because of difficulties in its dyeing and printing. In this work, carrier dyeing of polyphenylene sulphide fabric with disperse dye is discussed, and the effect of the structure of the carrier, dyeing temperature, dyeing time, usage of carrier and usage of dye on colour strength of the dyed sample and the percentage of dye exhaustion were investigated. In addition, the glass transition temperature, crystalline structure and orientation degree of treated polyphenylene sulphide fibre with benzyl benzoate were measured by differential scanning calorimetry, X‐ray diffraction analysis and velocity‐oriented tester, respectively. The results indicated that benzyl benzoate could increase the percentages of dye exhaustion and colour strength values, while at the same time reduce the glass transition temperature and orientation degree of the treated polyphenylene sulphide fibre. Thus, it would be beneficial to the diffusion of the dye molecules into the amorphous region of the fibre. Furthermore, the decrease of tensile strength and limiting oxygen index of the dyed polyphenylene sulphide sample was very little, and the colour fastness and levelness of the dyed polyphenylene sulphide samples were also satisfactory.     

An analysis of the substantivity of hydrolysed reactive dyes and its implication for rinsing processes

Substantivity plays a key role in dyeing processes, for dye exhaustion and fixation as well as for dye removal during rinsing. The latter is especially relevant for reactive dyes when the hydrolysed dye has to be removed from the fibre. The substantivity of the hydrolysed form of 46 commercially important reactive dyes was analysed at two temperatures for a wide range of dye amounts, pH values and electrolyte concentrations. The results showed that substantivity was highly dye‐specific and varied, for each variable analysed, almost within the entire theoretically possible range of values. Substantivity values correlated best with the number of sulphatoethylsulphone groups in the dye molecule and dye solubility in the presence of sodium chloride. Sensitivity to electrolyte, pH, dye amount and temperature broadly correlated with each other, implying that a reduction in electrolyte concentration and an increase in pH and temperature are more beneficial in the removal of highly substantive reactive dyes. Some dyes remained highly substantive even at 90 °C, indicating that dye removal in industrial processes, too, would be difficult. For dyes with little substantivity, however, wash baths at the boil do not appear to be necessary, neither is the significant removal of electrolyte before rinsing at elevated temperature.     

Some Fundamental Aspects of Transfer Printing

Conventional studies of integral sorption rates to determine diffusion coefficients cannot be applied to transfer printing. A simple technique based on the Daynes time–lag method is described which allows the steady–state diffusion coefficients of dyes to be determined under conditions of transfer printing. Both diffusion coefficients and activation energies of diffusion are similar to those found in vapour–phase and heat–fixation methods of dyeing. The saturation values and extent of fibre–bundle penetration by dye vapour are discussed in terms of dye flux to the surface and mean free–path lengths over a range of ambient pressures.     

Carrier Dyeing of Polyester Fibre Part III – The Role of Water in Solvent Dyeing

The role of water as an auxiliary in solvent dyeing of polyester fibre has been studied. The addition of water results in a lowering of the glass transition temperature, an increase in the diffusion coefficient and reductions in the energy of activation of diffusion and the entropy of activation of diffusion. The increase in the diffusion coefficient is smaller at higher temperatures and varies from dye to dye, being related to the energy of activation of diffusion. These effects are similar to those reported previously for carriers in the aqueous dyeing of polyester fibre and demonstrate that the role of water in solvent dyeing is similar to that of a carrier in aqueous dyeing.     

Structural, Physicomechanical, and Sorption Properties of Ternary Acrylonitrile Copolymer Fibres

When itaconic acid (IA) is replaced by vinylcaprolactam (VCL) in ternary AN:MA:IA (acrylonitrile:methyl acrylate:itaconic acid) copolymers, fibres similar in structure to industrial Nitron fibre are obtained, and they have a higher capacity for orientation the larger the amount of VCL added to the copolymer. The fibres obtained have higher physicomechanical properties and higher hydrophilicity and dyeability with disperse dyes than Nitron fibres. The values of the diffusion coefficient of equilibrium-sorbed dye, activation energy, and some thermodynamic properties are calculated. An increase in the VCL content in the copolymer and an increase in the temperature cause an increase in the degree of fixation of the disperse dye in the fibre. In ordinary dyeing conditions, a high residual dye content in the fibre can be attained.     

Basofil纤维分散染料染色性能研究

选择了4只蒽醌结构和2只偶氮结构的分散染料，用于Basofil纤维的染色，用0.5molHCl和DMF在高温条件下将纤维上的染料萃取完全后、染料的最大吸收峰不变：在染色达到平衡时，测定了纤维上染料的浓度，结果显示：分子结构小、具有共平面的蒽醌染料适合上染Basofil纤维。染料的扩散系数和扩散活化能随染色温度上升而明显增加，其中C.I.Disperse Blue 56在纤维中扩散速度最快实验结果表明：染料的分子结构越小，染料上染量越大，扩散系数和扩散活化能的研究也揭示了相同的规律.     

Carrier Dyeing of Polyester Fibre

Aspects of the diffusion of carriers in polyester fibre have been studied using several compounds representative of commercial carriers. The apparent diffusion coefficients, activation energies of diffusion, and entropies of activation of diffusion have been determined. The apparent diffusion coefficients were found to be several orders of magnitude greater than those of disperse dyes, whilst the apparent activation energies and entropies of activation of diffusion were lower. A major difference in the diffusion behaviour of carriers, compared with that of disperse dyes, is the concentration–dependence of the diffusion coefficients of the former class of compound.     

Dyeing kinetics of methacrylic acid grafted polyester fabric with astrazonrot violet and rhodamine red basic dyes

The low‐temperature dyeing kinetics of radiation‐grafted poly(ethylene terephthalate) fabric were studied. The effects of the graft yield (GY), dye concentration, and dyeing temperature on the color difference (CD) of methacrylic acid grafted polyester fabric were studied for astrazonrot violet (AV) and rhodamine red (RR) basic dyes. CD increased sharply with an increase in GY and tended to level off at higher degrees of grafting. The best dyeing conditions were achieved for both dyes at pH 11.5. CD of the grafted fabric increased rapidly as the dyeing time increased; this was followed by a relatively slow dyeing rate within a few minutes, which depended on the concentration and temperature of the dye bath. The initial dyeing rates and rate constants for the AV dye were higher than those for the RR dye. The dyeing process followed 0.14‐order kinetics and was independent of the dyeing temperature or the type of dye. The dyeing rates and rate constants increased with an increase in the dyeing temperature. An Arrhenius‐type plot of the natural logarithm of the dyeing rate constant versus the inverse of the absolute temperature yielded apparent activation energies of 4.9 and 13.8 kJ/mol and pre‐exponential rate constants of 9.4 and 100.6 (CD/GY)s^?1 for the AV and RR dyes, respectively. The mechanism of the dyeing process for the two dyes was diffusion‐controlled, and their dyeing rates depended on the type of basic dye. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1070–1076, 2004     

An Experimental Study of the Dyeability of Barry Nylon Fibre with Acid Dyes

When nylon fibre is dyed with acid dyes, the rate of diffusion into the fibre depends on the draw to normal ratio than for one more highly drawn. The ratio of the diffusion coefficients for two such substrates is independent of both the dye used and the amount of dye fixed on the fibre. The differences which appear in the dyeing of barry nylon textiles relate to the time parameter Dt/r² (D is the diffusion coefficient in cm² /s, t, the dyeing time in s, and r, the substrate radius in cm). The greater this parameter, the better is the coverage of barriness arising from variations in the draw ratio. Since the diffusion coefficient for a given substrate is specific to the dye, acid dyes differ in their suitability for dyeing barry nylon textile fabrics.     

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.     

Diffusion properties of reactive dyes into net modified cotton cellulose with triazine derivative

Cotton fabric is chemically modified with a 1,3,5‐triazine derivative containing multireactive and multicationic groups. The diffusion properties of the reactive dyes into net modified cotton cellulose are investigated. When the dyeing temperature is raised, the dye uptake increases gradually and approaches equilibrium after dyeing for 60 min. The diffusion coefficients at different temperatures and the activation energy of the dye are discussed. Compared with unmodified cellulose, the diffusion kinetics of the dye in the net modified cotton cellulose show significant changes. The activation energies of dyes in net modified cotton fibers are much lower than those of dyes in unmodified cotton. The dyeing behavior of the modified cotton is analyzed and compared with the unmodified cotton. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2166–2171, 2007     

The Physical and Chemical Properties of Reactive Dyes and their Effect on Printing Behaviour

The currently available methods of fixation of prints on textiles are reviewed and the influence of the reactivity, diffusion coefficient and substantivity of reactive dyes on their behaviour in printing is described. It is shown how the suitability to the various fixation methods and the stability in alkaline printing paste of reactive dyes can be correlated with the values of reactivity, diffusion coefficient, and substantivity measured by simple techniques. Changes that can be made to the reactivity of a dye by modification of its structure or its application conditions are also illustrated. The influence of hydrolysis of reactive dyes and of breakage of the dye–fibre bond during processing on the fixation achieved is discussed and a method is developed enabling the actual rate of reaction of reactive dyes with cellulose to be calculated.     

Some Observations on the Relation between Dyeing Properties and Fibre Structure

The processes by which dye is transferred from the liquor to the fibre are discussed briefly. Dyes and fibres are complex in structure and most dyeing systems are multicomponent; thus any attempt to correlate the chemical structure of a fibre and the chemical structure of the dyes that are used to dye it will probably have limited success. A simplified classification of some dyeing systems is given. In general, dye-fibre systems may be divided into non-ionic and ionic systems, the latter being subdivided into ionic systems with like and those with unlike charges. These systems are discussed. Structural features of the fibre that may influence the equilibrium sorption of dye are given and the effects of fibre structure on the kinetics of dyeing are considered. The dye-fibre system is analysed. There is no ‘theory of dyeing’ that can adequately describe practical behaviour.     

Diffusion of disperse dyes into microfibres and conventional polyester fibres

The dyeing properties of polyester microfibres are quite different from those of conventional polyester fibres. In this paper, the sorption isotherms, the diffusion coefficients and the amount and rate of dye uptake into the fibres are compared for both conventional fibres and microfibres. Shibusawa's approximation of Hill's equation is used to compute the diffusion coefficient, which depends on the initial dye concentration, the time and the fibre count for a fixed temperature (130 °C). The kinetic properties are analysed only under infinite bath conditions. The sorption isotherms and diffusion coefficients as functions of time for conventional polyester fibres and microfibres are compared by considering the surface area and the diffusional boundary layer influence.     

Activation Energies of Light Fading of Non–ionic Disperse Dyes in Hydrophobic Polymers

Eight non–ionic (disperse) dyes adsorbed in films of cellulose acetates, nylon and poly(ethylene terephthalate) (PET) have been faded by visible and near–ultraviolet radiation at temperatures in the range 15 to 100°C, and in atmospheres of relative humidities (r. h.) from zero to saturation. Fading is accelerated by rise in temperature, and, at r. h. above 5%, by rise in r. h. Activation energies of fading (Ef) (r. h. > 5%) range between about 3 and 18 kcal/mole, and depend on the nature of the substrate rather than on the structure of the dye. Values rise with increasing crystallinity of the polymer structure, except for PET which gives anomalously low values. The extent of dye–fibre interaction is at a minimum with PET and the rate–controlling step is a purely photochemical one. With the other substrates, the rate of fading is controlled by the dye–substrate interaction. The accelerating action of atmospheric humidity over normal ranges is partly due to its influence on the dye–substrate bonding and partly to its effect in swelling the substrate and thus increasing the diffusion coefficient of oxygen.     

New insights into dye chemistry and physics

A review of the academic dye research performed by the Port Sunlight group and its coworkers over the past 15 years is presented. The work is focused on three areas: (1) substrate structure; (2) dye interactions in aqueous solution and on substrates; (3) dye degradation and products. For substrates, a detailed model of the nanoenvironment experienced by chemicals within cellulose fibre is given, showing the different environments and remarkable mobility of absorbed chemicals. Advanced nuclear magnetic resonance diffusion measurements provide the complex pathways by which compounds find their way in and out of the fibre. For dye interaction, detailed theoretical and experimental studies are reported on three model dye systems, the anionic monoazo dye Orange II, the bisazo anionic dye CI Direct Blue 1, and cationic monoazo thiazolium dyes, providing a comprehensive picture of their structure. A quantitative mechanism of dye binding to cellulose is shown. Resonance Raman provides an effective forensic tool for dye identification, even from single fibres. The products and kinetics of Orange II dye degradation by one‐electron reduction in aqueous solution is given, with the identification of an indophenol dye end‐product. In cellulosic materials the reduction mechanism is similar to solution, when the higher microviscosity is accounted for. Hydrolysis of thiazolium dyes occurs at both aromatic rings of the dye but on different timescales. Measurement and calculations of the electronic structures of one‐electron‐reduced and ‐oxidised dyes are presented. The mechanism of photooxidation by sunlight of azo dyes in cotton is delineated.     

The Effect of Carriers on the Crease Recovery of Poly(ethyleneterephthalate) after Heat-setting

The presence of carriers in polyester fabric reduces the temperature at which creases become permanently set. The magnitude of the effect depends on the concentration of the carrier in the fibres, the time and temperature of heat-setting and the chemical structure of the carrier.     

Modelling cationic dyeing-consideration of ionic and hydrophobic interactions in a modified Donnan approach

A modified Donnan model has been derived, based on hydrophobic and ionic interactions between dyes and fibres. This model gives a good prediction of a cationic dye equilibrium sorption on an acrylic fibre under different dyeing conditions. The decrease in dye sorption with increasing salt concentration, followed by an increase in the dye sorption following further increase in the concentration of some salts (such as sulphates and phosphates), can be interpreted by this model. The study provides a quantitative approach to the dual functions of simple electrolytes during cationic dyeing, i.e. the competition of sorption sites with dyes through ionic interactions and the promotion of the dye sorption through hydrophobic interactions.