Dyeing mechanism and model of nylon 6 fiber dyeing in low‐temperature hydrogen peroxide–glyoxal redox system

This article reports the results of a study of nylon 6 fiber dyed in a low‐temperature hydrogen peroxide–glyoxal redox system. It was expected that the dyed fiber would have better dye fastness and higher economic value than would conventional fiber. In addition, this article presents the proposed mechanism for and model of a free‐radical dyeing system as well as a derived theoretical equation. From the experimental results, it was found that formation of covalent bonds by the coupling of the dye and the fiber radical in free‐radical dyeing was only 25%–40%, whereas with the conventional type of ionic dyeing, it was almost 60%–75%. Because the initiation efficiency of free‐radical formation is affected by many factors, such as the pH of the dye bath and the concentrations of the oxidant and reductant, the aims of this study were to investigate the formation of free radicals and the effects on dye uptake of the concentrations of dye, oxidant, and reductant and of the fiber amine end group. In addition, the dyeing properties of dyed fiber were investigated, and the dyeing order and rate constant of the rate equation were evaluated from the experimental data. From the experimental results, the following conclusions were drawn. (1) The hydrogen peroxide–glyoxal redox system produced many free radicals in the dye bath as temperature reached 70°C. (2) The amine end group in the nylon fiber was the main site of ionic and covalent bonding between nylon 6 fiber and dye. (3) The proposed model of free‐radical dyeing showed, from the fit of the experimental data into the equation and the evaluation of the equation parameters, that the order fit the theoretical value well, with the rate constant dependent on the dyeing conditions; at pH = 3, it could match the equation's best (rate equation of the proposed model: d[D]_R/dt = k_A[GO]¹[H₂O]^m[D]^1/2[F]^1/2). (4) The optimum dyeing conditions in the hydrogen peroxide–glyoxal redox system were: [H₂O₂] = 0.15–0.20M, [glyoxal] = 0.07–0.10M, pH = 3, dyeing temperature = 70°C, and dyeing time = 45–50 min. (5) The redox dyeing system had better dye fastness than did the conventional system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4197–4207, 2006     

Dyeing of cotton with the natural dye extracted from waste leaves of green tea (Camellia sinensis var. assamica)

Due to an increase in the production of green tea, the amount of leaf waste has increased enormously, causing serious environmental problems. With regard to environmental awareness, the possibility of reusing the waste leaves of green tea as a low‐cost and abundantly available source of natural dye for dyeing cotton fibres was investigated. Natural dye powder from the waste leaves of green tea (NDPT) was successfully applied to dye cotton fibres without mordant by batch experiments. NDPT was obtained as a dark brown powder with a yield of 2.7 ± 0.5% w/w from dried waste leaves of green tea. The optimal conditions for dyeing NDPT onto cotton fibres were: pH of dye solution, 3; material to liquor ratio, 100:1; dyeing time, 180 min; concentration of dye solution, 3.0 mg/ml; and dyeing temperature, 100 °C. The colour of cotton fibres dyed with NDPT was observed to be dark brown. The adsorption data of NDPT on cotton fibres was best fitted with a Langmuir adsorption isotherm model with a correlation coefficient (R²) of 0.997. It is clear that there is a strong possibility of reusing the waste leaves of green tea as a low‐cost and abundantly available source of natural dye for dyeing cotton fibres.     

Physico–chemical and Dyeing Properties of Disperse Dyes containing Phthalimide Residues

The relationship between the constitution and the physico–chemical and dyeing properties of disperse dyes containing phthalimide residues has been studied. The influence of the –NH or –NCH₃ group in the phthalimide residues on the thermal and spectral properties of dyes has been investigated. Their influence on the dyeing process and on the colour and fastness properties of dyed polyester have also been studied.     

Kraft lignin degradation products for tanning and dyeing of leather

Kraft lignin degradation by a biomimetic system was investigated, using hemin as a catalyst and hydrogen peroxide as an oxidising agent, which mimics the catalytic mechanism of lignin peroxidase (LiP) to produce phenolic compounds. The degradation products were identified using spectroscopy and gas chromatography–mass spectrometry (GC–MS): 2‐methoxyphenol, 4‐hydroxybenzaldehyde, vanillin and vanillic acid were produced and their formaldehyde polymerisation products used for tanning hide powders. The denaturation (shrinkage) temperature of hide powder was raised to 80 °C through hydrogen‐bonding interactions between the polymers and the collagenic hide powder. For dyeing of hide powder, the lignin degradation products were reacted with laccase (a polyphenol oxidase): 2‐methoxyphenol gave the darkest colour. These products have potential to be used as raw materials for tanning and dyeing of animal skins. Therefore, value can be added to this industrial byproduct and reduce its environmental impact. Copyright © 2004 Society of Chemical Industry     

Vapour–phase Dyeing of Synthetic–polymer Fibres

Absorption isotherms at high temperatures for some disperse dye vapours and secondary cellulose acetate film have been determined and found to be linear. In order to calculate dye vapour concentrations, two methods have been used for the determination of vapour pressures, and from the results it is shown that disperse dye molecules can associate in the vapour phase. The absorption of dye vapour by polyester fibre in the form of small packages over the range 180–220°C, as well as a laboratory machine that can be used for this purpose, are described. Package dyeing on a larger scale with dye vapour is considered to be possible.     

Dyeing of silk fabric with phenazine from Pseudomonas species

Phenazines, namely oxychlororaphin and pyorubin, were extracted from Pseudomonas sp., purified and their dyeing potential as colorants for silk dyeing were examined. The effects of the process variables, such as phenazine concentration, pH, temperature, time, type of mordant, relative colour strength and fastness properties have been studied. The results showed that the optimum condition for dyeing was 90 °C at pH 3 and dyeing time 90 min for oxychlororaphin, and 70 °C at pH 3 and dyeing time 60 min for pyorubin. The K/S value of a pre‐mordanted silk fabric with oxychlororaphin was high when compared to that with the pyorubin. The antimicrobial activity of a dyed silk fabric was tested against Salomonella paratyphi, Escherichia coli and Shigella flexneri.     

Energy‐efficient dyeing of nylon 6 using indigo powder dyestuff after atmospheric plasma treatment at ambient pressure

Nylon 6 was treated with a dielectric barrier discharge, i.e. atmospheric plasma at ordinary air pressure. Factors influencing the dyeing process of nylon 6 using indigo blue powder were studied. The mechanism and effect of this dyeing technology were compared with those of conventional technology. Dyeing after plasma treatment at 30–50 °C can produce high dye uptake in a short time. Notably, dyeing after plasma treatment is beneficial for energy conservation. However, at 60–70 °C, the K/S values of plasma‐treatment dyeing sharply increased over a short time, after which they remained largely unchanged. This finding indicated that the dyeing mechanism changed. The speed constant of dyeing after plasma treatment is 2.8 times that of conventional dyeing. The K/S values of dyeing samples after plasma treatment approached the dyeing saturation K/S value in a short time; therefore, this method of dyeing after plasma treatment achieves energy conservation and efficiency in a brief period of time. Conversely, conventional dyeing is more effective at high temperatures but consumes more energy. The adaptive electro‐discharge condition is achieved under the treatment conditions of 375 W for 2 min. The chromatic aberration of the dyed samples after plasma treatment is smaller than that of conventional dyeing at 50 °C for 75 min.     

Dyeing properties of wool treated with liquid ammonia

Wool fibre and fabric have been treated with liquid ammonia and their surface characteristics investigated by means of SEM and ESCA techniques. The treated specimens were dyed with levelling and milling acid dyes. Although no changes in nitrogen content and fibre surface properties were detected, their dyeing rate was increased considerably as was saturation dye exhaustion. Dyeing properties were similar to those of wool treated with low-temperature plasmas by glow discharge. Fabrics treated with liquid ammonia were dyed at various temperatures in the range 30–80°C, and dye uptake was similarly increased.     

Development of a Solvent Process for the Dyeing of Wool Sliver

The development is described of a prototype machine for dyeing wool continuously in 75 % formic acid at 50–60d?C, with recovery of the formic acid by distillation. A complete plant for treating 8000 lb of wool per day of two shifts was estimated to cost $A120,000 (£55,000). Excluding the cost of dyes and further processing, dyeing wool on this scale of operation was estimated to cost 70 cents (7-7 d.)per lb, and at 200,000 lb per day with three-shift operation 5-3 cents (5–8 d.)per lb. The very even uptake of dye obtained in formic acid would be expected to result in further savings on the cost of recombing after dyeing.     

Polynomial Approximations Describing Rate of Dyeing from a Finite Bath

Three polynomial approximations to Wilson's equation were derived by means of Hastings's method. One of them is an approximation to Crank's equation with 3–figure accuracy and it approximates to Wilson's epuation very closely for high values of fractional equilibrium exhaustion (E), E > 0. 95. Two other polynomials approximate to Wilson's equation very well in the ranges 0. 95 > EX). 76 and 0. 76 > E > 0. 30 respectively. The polynomials derived here only include up to second order terms, so that by using the equations which are obtained by solving the polynomials for diffusion coefficient (D), D can easily be calculated from experimental dye uptake data. By using the polynomial approximation, the changes in rate–of–dyeing of a non–ionic dye on a nylon 6 fibre by addition of a dispersing agent were calculated. Results of the experiment agreed well with the calculated.     

Dyeing properties of silk produced by silkworms reared on artificial and mulberry leaf diets

The dyeing properties were investigated for silk proteins produced by silkworms reared entirely on an artificial diet (A) and a mulberry leaf diet (M). The dyeing experiments were carried out with CI acid orange 7 at pH 3.9 and 60°C. The sericin contents of the A and the M raw silk samples were determined to be 26.0% and 23.7%, respectively. The equilibrium dye uptake and the dyeing rate of the A silk fibroin were almost the same as those of the M silk fibroin. The equilibrium dye uptake on each silk sericin was 3–4 times higher than that of the silk fibroin. On the other hand, the equilibrium dye uptake of the A silk sericin was higher than that of the M silk sericin, but the dyeing rate of the former was slower than that of the latter.     

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     

Molecular Mechanisms of Disperse Dyeing of Polyester and Nylon Fibres

The kinetics of the dyeing of polyester fibres with disperse dyes have previously been discussed in terms of a model in which the only forces of interaction between dye and polymer are those that give rise to mutual solubility. The rate and extent of dyeing depend on the size and shape of the dye molecules and the detailed structure of the fibre. The concentration profiles of dye within single filaments of polyesters and nylons have now been determined by a new method termed ‘optical sectioning’, in which an image of a filament is scanned by a narrow slit. The dye distributions are found by comparing experimental transmission values with those calculated by a computer for a model system in which various parameters can be adjusted. For the polyester-dye systems the rate constant of transfer of dye from dyebath to fibre (k₁) was the same as the rate constant of diffusion away from the interface (k₂). Some nylon-dye systems, on the other hand, behaved as if k₂ = k₁, whereas others behaved initially as if k₁ = k₂ but later as if k₂ > k₁. Apparent diffusion coefficients were also derived from sorption measurements and were found to fall as the dye concentration in the fibre increased. Measurement of the orientation of the dye molecules by optical dichroism showed that the dye molecules entering the filaments late in the dyeing process were more highly orientated than the earlier ones. The decrease in diffusion coefficient has been interpreted in terms of the observed higher orientation, as resulting from a greater entropy of activation in the diffusion process.     

Dyeing of poly(lactic acid) fibres with synthesised novel heterocyclic disazo disperse dyes

Poly(lactic acid) (PLA) is the first melt‐processable, renewable, sustainable and biodegradable natural‐based synthetic fibre. It has a broad range of uses and combines ecological advantages with outstanding performance in textiles. PLA fibre, as an aliphatic polyester, can be dyed with disperse dyes. Apart from the limited number of commercial disperse dyes, disperse dye exhaustion on PLA is generally lower than that on  poly(ethylene terephthalate) (PET). In this study, new heterocyclic disazo disperse dyes, substituted with methyl, nitro and chloro groups at their ortho‐, meta‐ and para‐ positions, synthesised in our previous study, were applied to PLA and PET fibres to examine their dyeing performance, and colour fastness and dye exhaustion properties. Different shades of yellow, orange, reddish brown and brown were obtained. Most of the synthesised novel heterocyclic disazo disperse dyes exhibited good build‐up properties with high K/S levels on both fibres. Para‐ bonding substituent provided higher K/S values than meta‐ and ortho‐ positions for –NO₂ and –Cl substituents for both fibres. Overall, the most synthesised novel heterocyclic disazo disperse dyes in this study exhibited good build‐up properties with high K/S, exhaustion and wet fastness levels on both PLA and PET fibres.      

Dyeing Properties of a Polyamide–Epichlorohydrin Resin

The dyeing behaviour of cured films prepared from a polyamide–epichlorohydrin resin (Hercosett) was examined in orderto obtain a better understanding of the dyeing beha viour of Hercosett–treated wool. The polymer films swell by 500–1000%. The swelling decreases with increasing dye content in the polymer and with increasing temperature. The diffusion of acid dyes into the polymer is extremely fast (D =10^-7 cm²/s), and can be accelerated by the addition of salt. The sorption of the dye is described in terms of a Langmuir isotherm, indicating that an ion–exchange mechanism is operative. The concentration of cationic groups in the polymer is very high (2. 4mo//kg) and does not depend on the curing conditions. The addition of salt reduces the exhaustion of the dyebath. Reactive dyes were found to be bound covalently to the resin. During industrial resin treatment it has been shown that the molecular weight distribution of the Hercosett in the resin bath changes markedly, molecular weight increasing with running time and the spread of values being much narrower. This may explain the variation in the dyeing behaviour of wool fibres that have been treated at different times in the same resin bath.     

Dyeing fine denier polypropylene fibers with phenylazo- β -naphthol-containing sulfonamide disperse dyes

A series of phenylazo-β-naphthol-containing sulfonamide disperse dyes were prepared from C.I. Acid Orange 7 by successive reactions of chlorination and amination, and their chemical structures were characterized by FTIR, ¹H NMR, and mass spectrometry. The dyes were applied to coloring of knitted fabrics from fine denier polypropylene fibers by exhaust dyeing and their optimal dyeing conditions, such as dyebath pH, dyeing temperature, dyeing time, and dye concentration were investigated in detail. Then, dye exhaustion, color strength, and color fastnesses of the dyes on the fibers were assessed and summarized. In view of dye exhaustion and color strength of the sulfonamide dyes on fine denier PP fabrics, 90°C was selected as the best dyeing temperature at dye concentration below or equal to 3.0% owf. For achieving higher color strength, 130°C was the better choice when the dye concentration was above 3.0% owf. The sulfonamide dyes, especially secondary sulfonamide dyes, exhibited superior dye exhaustion and color fastnesses to washing, sublimation, and rubbing on fine denier PP fabrics in comparison to C.I. Solvent Yellow 14 bearing the same chromophore but without sulfonamide group.     

阳离子染料可染改性涤纶纤维染色的研究

从纤维结构及染色工艺对阳离子染料可染涤纶纤维的染色性能进行了研究。探讨了染料用量、pH值、匀染剂用量、和染色时间对染色的影响。通过对比试验得出最佳染色处方和工艺条件为：染料用量0．5％（o．w．f），pH值3．5—4．5，醋酸钠1％（o．w．f），匀染剂12270．5％（o．w．f），浴比1：30，100％染100分钟...     

聚苯乙烯/苄基木粉复合材料的染色研究

在三氯甲烷(CHCl3)中,将苄基木粉与聚苯乙烯(PS)泡沫塑料复合制得PS/苄基木粉木塑复合材料(WPC),探讨了分散染料对其染色的效果,并用红外光谱和扫描电子显微镜对WPC进行结构分析。结果表明,PS/苄基木粉复合材料能被分散染料染色,分散染料的分子结构和相对分子质量大小是影响分散染料上染速率的2个重要因素,染色PS/苄基木粉复合材料的色光近似于染色聚酯织物,且均随染色温度的升高、染料浓度的增大而变深,分散染料的上染率和染色木塑粉的耐水洗牢度随染料浓度的增大而下降,随染色温度的升高而升高。     

Dyeing of Texturised Polyester Yarn

The paper describes a study of many factors which play a significant part in the dyeing of texturised-polyester yarn at high temperatures. The variables chosen for study are the selection of disperse dyes to give the desired fastness properties, coverage of dyeing-substantivity differences before, during and at the end of the dyeing process. The effects of different types of dispersing agents on dispersion properties and the selection and behaviour of different types of ‘carrier’ suitable for high-temperature dyeing are also considered, the latter in relation to levelling, dye yields, ability to compensate for small differences in dyeing temperature, coverage of yarn variations, minimisation of dye and oligomer crystallisation at the end of dyeing and the stability of the ‘carriers’ themselves. The formation and behaviour of oligomer have also been investigated. Factors governing the choice of optimum dyeing cycles for polyester yarn are also reviewed.     

Bulk–scale Dyeing of Acrylic Yarn Packages

Bulk–scale dyeing trials on three different types of acrylic fibre are described. Basic dyes were applied under conditions predicted to give a borderline degree of unlevelness, following earlier laboratory work [1–3] intended to determine the relative importance of different factors which control level dyeing in this system. The results of the dyeing trials are discussed in this context and an attempt is made to attribute the effects observed to specific causes of unlevel uptake of dye.