Deep‐colour vat dyeing of cotton knit fabric on a modified jet dyeing machine

To improve the vat dyeing of cotton knit fabric with Indanthren Black RB Coll. (CI Vat Black 9), the basic parameters of dyeing, including the concentrations of chemicals, the dyeing temperature and duration, and the apparent diffusion coefficient of the dye, were obtained by test dyeing with a stoppered Erlenmeyer flask and the cellophane film roll method. A stable vat dyeing process has been developed on a modified jet dyeing machine for the first time without using nitrogen to purge oxygen. Modifications were made to improve the airtightness of the machine and the equipment in the liquor circulating system, with a water inlet and outlet for the gentle oxidation of dyed fabric, and with monitoring by means of a sensor inserted in the liquor circulating system for in situ measurements of the redox potential and the pH of the dyeing liquors. These measurements made it possible to follow to their completion the process of dyeing and the process of gentle oxidation by overflow washing with water and final oxidation. Optimal conditions with regard to the amount of reducing agent, the dyeing temperature (80 °C), and oxidising processes were established with this machine. It was found that, by using the modified machine and process conditions, dyeing proceeded stably and reproducibly (at 80 °C) to yield grade A dyed fabric. Visual inspection confirmed that faultless deep‐colour dyeing of the fabric was attained. Production has been proceeding successfully for the past 2 years. Owing to its insolubility, complete removal of the dye from the wastewater has been possible.     

偶氮染料的光还原脱色及其染色废水的回用研究

用还原脱色剂对水溶性偶氮染料进行光还原脱色降解,重点考察了还原脱色剂、辐射光以及染料浓度等对还原脱色反应的影响,并将脱色后的染色废水回用于棉织物染色中.结果表明,以适当比例的引发剂和促进剂组成的还原脱色剂具有较强的脱色降解能力,辐射光对染料的还原脱色反应具有明显的促进作用,染料浓度的提高不利于染料的脱色降解反应.脱色废水可以回用于棉织物的活性染料染色中,通过降低染色过程中氯化钠和碳酸钠的添加量,可使染色试样与自来水染色试样的总色差(DE*)＜1.0.     

Application of rare earth as mordant for the dyeing of ramie fabrics with natural dyes

Selecting appropriate metallic compounds as mordants is essential for dyeing with natural dyes. This paper presents the application of rare earth compounds as mordant for the dyeing of ramie fabrics with four kinds of natural dyes. The influences of pre-mordanting, simultaneous mordanting, and post-mordanting on the dyeing effect were explored. The post-mordanting was proved to give rise to the highest dye uptake. The effects of dyeing conditions including dyeing temperature and time, dyeing bath pH and the concentration of rare earth on the dye uptake were investigated systematically. The fabrics dyed with natural dyes in presence of rare earth as mordant exhibited high color shade stability in the baths with pH varying from being acidic to neutral and alkaline. Employing rare earth as mordant apparently raised the color fastness to washing, rubbing and light of the ramie fabrics dyed with the natural extracts. In comparison with the commonly used metallic salts, using rare earth chlorides as mordants can greatly reduce the ionic concentration employed in natural dyeing. This study proved that rare earth would be a kind or promising environmentally friendly mordant in natural dyeing.     

Improving the dyeability of polyimide by pretreatment with alkali

Polyimide fabric, as a high‐performance fabric, possesses advantageous properties, such as outstanding thermal stability and chemical resistance, but has poor dyeability. In this paper, polyimide fabric was dyed successfully with disperse dyes by high‐temperature and high‐pressure dyeing in the presence of a swelling agent and auxiliaries. Under optimal dyeing conditions, it is pretreated with NaOH 6 g l^?1 and dyed with disperse dyes 5% o.w.f., NaCl 1 m , benzyl alcohol 60 ml l^?1 at 135 °C for 45 min to obtain a satisfactory colour yield with good washing fastness and dry rubbing fastness with 93.3% strength retention. The experimental results demonstrate that the Nernst adsorption isotherm is a favourable model for polyimide fabric dyeing with disperse dyes.     

Application issue of anthraquinonoid vat dyes on inherently flame-resistant fabrics

The vat dyeing process of specific fabrics with protective, inherently fire retardant properties that have a high content of aramid fibres in their composition, is presented. The research was performed on fabric samples that differ in raw material composition and aramid content. The samples were dyed in raw form (group 1) as well as after pretreatment with alkaline scouring (group 2). Measured limiting oxygen index (LOI) values showed that the selected fabrics meet the properties of inherently fire retardant fabrics. Dyeing was performed with Indanthren® Olive Green HB (manufactured by DyStar) vat dye, in exhaustion process, with a bath ratio of 1:30. The dye concentration was 3%, and sodium-hydrosulphite (Na₂S₂O₄) was used as a reducing agent. The colouristic analyses were performed based on spectrophotometric measurement and results interpretation according to CIELab system. The evaluation of primary tactile properties was performed which show an increase of smoothness and softness after scouring and dyeing. Also, wash fastness as well as light fastness tests have shown satisfactory fastness properties.     

Colour of flax fibres in regard to different pretreatment and dyeing processes

The main objective of this work was to compare the colour of different pretreated (alkaline, acidic and enzymatic) and dyed (conventional and ultrasonic-assisted) flax fibres, to establish the impact of various parameters on dyeing kinetics. Flax fibres were dyed using two direct dyes of different chemical structures and molecular mass. Diffusion profiles were established by the application of Fick's Law and dyeing behaviour was studied by means of online spectrophotometry. Finally, the dyed samples were colorimetrically evaluated and colour differences and colour strengths were subsequently calculated. The results provided evidence that a dye molecule's size has a greater influence on the exhaustion degree, migration and diffusion than individual pretreatment processes. The determined diffusion coefficients indicated superior dye mobility and faster diffusion into the fibres when ultrasonic power was used in comparison with conventional process. Nevertheless, the colour depth obtained was found to be low after ultrasonic dyeing using a larger dye molecule, implying part degradation of CI Direct Red 80 (and total degradation of small-size dyestuff, CI Direct Red 81).     

Colour variation in the dyeing of denim yarn with indigo

In this paper, various parameters of warp yarn dyeing using indigo dyes are investigated. These parameters include dye concentration, number of dips in the dyeing process, dyebath pH, amount of reducing agent, immersion time, oxidation (skying) temperature, effects of a wetting agent and soaping temperature. This study revealed that these parameters have varying degrees of influence on the resultant colour of the samples dyed. The degrees of variation in colour were expressed using the CIE L* a* b* system as well as the shade depth (Integ).     

Application of polycarboxylic acid sodium salt in the dyeing of cotton fabric with reactive dyes

In this study, the effects of polycarboxylic acid sodium salt on the dyeing of cotton with reactive dyes were evaluated by measuring and comparing the K/S values and dyeing fastnesses of the dyed cotton fabric samples. Results showed that the K/S value and dyeing fastness of cotton fabrics dyed with polycarboxylic acid sodium salt, substituting inorganic salts as exhausting agent were close to that of with sodium chloride when dip‐dyeing process was used. While, in pad‐dry dyeing, the K/S value of cotton fabric samples dyed with polyacid salts as exhausting agent was higher than that of with sodium sulfate, and the dyeing fastnesses of these samples were nearly the same. The dyeing mechanism of cotton fabric with reactive dye, using polycarboxylic acid sodium salt as exhausting agent was analyzed. The dyeing exhausting mechanism of reactive dye seems different when the inorganic salt and polycarboxylic acid sodium salt were used as exhausting agent in the dyeing of cotton fabric with reactive dye. The polycarboxylic acid sodium salt, as weak electrolyte, increased the dye‐uptake of reactive dye on cotton fabric not only by screening negative charges on cotton surface, but also by the effect of salting‐out or hydrophobic combination. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Application of sodium benzoyl thiosulphate from aqueous solution to wool and its effect on substantivity of disperse dyes. Part 1: synthesis and characterisation of sodium benzoyl thiosulphate

The introduction of bulky aryl residues into wool fibres not only enhances their disperse dyeability but also improves their settability, shrink resistance and imparts easy‐care properties. It would be highly desirable for colourists to achieve such effects when dyeing or printing wool from an aqueous solution as wool/polyester blend fabrics could be dyed and printed with the same dye; furthermore, in the case of an all‐wool fabric pretreated with such arylating systems, following dyeing or printing with disperse dyes, dye fixation can be achieved by dry heat procedures. A water‐soluble, fibre‐reactive arylating agent, sodium benzoyl thiosulphate, was therefore synthesised, characterised and its stability to hydrolysis in aqueous media was examined.     

涤纶常压染色促染剂的制备及应用

以有机碱三乙醇胺为催化剂,邻苯二甲酸酐(简称苯酐)与自制阳离子改性剂WLS反应,制备苯酯助剂,并将其作为涤纶分散黑ECT染料常压染色的促染剂。通过系统研究,优化出苯酯合成工艺,并探讨苯酯助剂与N-正丁基邻苯二甲酰亚胺(简称亚胺)复配对分散黑ECT常压染色性能的影响。结果表明:苯酯与亚胺有很好的协同效应,二者质量比按2∶1复配时,可获得最佳染色效果。该复配促染剂应用于涤纶常压染色中,染色后织物先进行195℃焙烘2.5 min,再还原清洗,织物的染色深度K/S值和上染百分率较常压无助剂、同条件染色工艺显著提高,而且基本达到传统高温高压的染色效果。     

Foam properties and application in dyeing cotton fabrics with reactive dyes

The foam dyeing of cotton fabric with CI Reactive Red 120 has been studied as a low‐add‐on technology. The foamability of different types of foaming agent and the stability of foam stabilisers were compared. Factors influencing foam dyeing, including wet pick‐up, fixation agent, foam stabiliser, and blow ratio, were evaluated by colour strength and dye fixation rate. Wet pick‐up, fixation agent, and foam stabiliser were found to be the main factors in the foam dyeing process. The comparative build‐up properties, dyeing properties, and total consumption between foam dyeing and conventional dyeing were assessed. The results indicate that, in foam dyeing, the dyestuff has a better build‐up property, the dyed fabric has excellent wash and rub fastness, and large amounts of water and energy are saved. Moreover, foam dyeing requires smaller dosages of chemical agents and reduces the difficulty of effluent treatment.     

Using ecological reducing agents instead of sodium sulphide in dyeing with CI Sulphur Black 1

Although low‐cost sodium sulphide is used as a reducing agent in most sulphur dyeing processes, it is considered to be environmentally unfavourable because of the resultant contaminated wastewater and the toxic hydrogen sulphide generated during the dyeing process. In the present paper, hydrazine sulphate, glucose, and sodium borohydride in the presence of sodium hydroxide were used as ecologically safe reduction systems for the CI Sulphur Black 1 dyeing of cotton fabric, and results were compared with those obtained using sodium sulphide. Dyeing processes were carried out at 90 °C for 60 min, and the colour yield (the K/S value), dyeing fastness, and breaking strength of dyed fabrics after soaping were measured. Response surface methodology was employed for experimental design and optimisation of results. Mathematical model equations were derived and statistical analysis carried out by computer simulation programming using Minitab v.15. At a dosage of 0.8 g l^?1 of CI Sulphur Black 1, the optimum sodium borohydride reduction system (sodium borohydride 0.47 g l^?1, sodium hydroxide 0.65 g l^?1) exhibited the highest colour yield and the lowest chemical oxygen demand of the residual dyebath.     

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     

Alkaline dyeing of polyester and polyester/cotton blend fabrics using sodium edetate

An alkaline dyeing of polyester with an alkali‐stable disperse dye, Dianix® Scarlet AD‐RG, was developed using sodium edetate as an alkaline buffering agent. The results obtained indicate the suitability of using sodium edetate for alkaline dyeing of polyester when compared with the control alkaline dyeing using Dianix AD system. Selected mono and bifunctional reactive dyes were used in combination with the alkali‐stable disperse dye for dyeing of polyester/cotton blend. Different dyeing methods for cotton and polyester/cotton blend fabrics using sodium edetate were evaluated in comparison with their respective control alkaline dyeing methods. The results of using sodium edetate in one‐bath two‐stage and two‐bath dyeing of polyester/cotton blend were comparable with that of the control dyeing method. Particularly, no change in the leveling and fastness properties was evaluated for all samples irrespective of the dyeing method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

乙醇-水体系中活性染料无盐低碱染色技术的探索

采用活性染料在乙醇-水混合溶剂体系中对棉织物进行染色、固色,探讨了碱预溶胀和一浴两步法两种染色方式及固色碱的种类、浓度、固色温度等对染色性能的影响,并与传统染色工艺比较。结果表明：在乙醇-水染色体系中,随着乙醇比例的增加,上染率增加;使用氢氧化钠和碳酸钠两种碱预溶胀棉织物后,相同浓度下,碳酸钠的固色率高于氢氧化钠,而且氢氧化钠的固色率随着浓度的增加而减小;一浴二步法染色中,采用80%体积分数的乙醇-水体系染色更符合实际生产的需求,氢氧化钠的适宜固色浓度为2g/L,碳酸钠的适宜固色浓度为3g/L;在乙醇水体系染色中,不需加盐,碱使用量为常规染色的1/10时,上染率为97%,固色率比常规染色高出9%~20%。     

Application of phthalimide-based alkali-clearable azo disperse dyes on polyester and polyester/cotton blends

Phthalimide-based alkali-clearable azo disperse dyes were synthesised and applied to polyester and polyester/cotton blends. These dyes have an alkali-clearable property that enables alkaline treatment to be substituted for conventional reduction clearing. Therefore, by using these dyes, it is possible to avoid generating dyehouse effluents with high BOD values and carcinogenic aromatic amines that may, in some cases, be liberated by reduction clearing. In addition, polyester/cotton blends can be dyed by a one-bath, two-step dyeing method, as alkali clearability enables the disperse and reactive dyes to be used in the same bath. The dyeing behaviour and fastness properties of these dyes have been investigated. In particular, the cross-staining of cotton was studied to estimate the suitability of the dyes synthesised for dyeing polyester/cotton blends.     

A novel and eco-friendly approach for dyeing polyester fabrics by liquid disperse dyes treated with deep eutectic solvent

Disperse dyes do not contain water-soluble groups and are difficult to dissolve in water, so they cannot be directly formulated into dyeing liquor. In the current dyeing process, the solubility of disperse dyes is mainly improved by adding dispersants. However, dispersants are not absorbed by fibres and survive in the dyeing effluent, aggravating the pollution of water bodies and causing difficulties in treatment. Therefore, the development of a novel, eco-friendly dyeing approach is important to overcome these problems. Herein, for the purpose of improving the solubility of disperse dyes and reducing the dosage of dispersants, a deep eutectic solvent consisting of choline chloride/ethylene glycol was employed instead of dispersant to dissolve CI Disperse Blue 79 and CI Disperse Red 343, thus forming liquid disperse dyes. The results show that both CI Disperse Blue 79 and CI Disperse Red 343 were well dissolved in choline chloride/ethylene glycol with excellent stability, and the dissolution behaviour was strongly associated with the dissolution temperature and time. Moreover, polyester fabrics can be dyed successfully with liquid disperse dyes, and it was observed that the K/S value and rubbing fastness were evidently improved at the same dyeing temperature with unchanged colour characteristics, and a higher K/S value could still be obtained by lowering the dyeing temperature. This work establishes a green dyeing process, which reduces dyeing costs and meets the demand for environmental protection. It is also expected to realise the liquid state of disperse dyes, which will help to promote the further development of textile dyeing.     

Cathodic decolourisation of textile waste water containing reactive dyes using a multi‐cathode electrolyser

The reductive decolourisation of textile dyestuffs containing an azo group was investigated by direct cathodic electron transfer CI Acid Red 27 and CI Acid Yellow 9 were used as model compounds for azo dyes. Reactive dyes, eg CI Reactive Red 4, CI Reactive Orange 4, and CI Reactive Black 5, which are in technical use for cellulose dyeing were investigated as representatives of practical importance. A basic characterisation of the reduction–decolourisation behaviour of the dyes was achieved by redox titration with Fe(II)–triethanolamine as reducing agent and parallel spectrophotometric observation of changes in the chromogenic system. From the redox titration experiments basic data describing the experimental conditions for successful cathodic electron transfer can be derived. The electrochemical dyestuff reduction experiments were performed in batch trials using a multi‐cathode electrolyser with high cathode area. According to the typical composition of such dyebaths 0.12 mol dm^?3 NaOH was used as ground electrolyte. The absorbance of the investigated dyestuff solutions could be decreased to below 20% of the initial value. For a 50% decrease in absorbance, electrical energy of about 6 kWh m^?3 is consumed. The process is of particular interest for the treatment of concentrated dyestuff solutions as they are used in continuous dyeing processes. © 2001 Society of Chemical Industry     

棉盖丙复合针织物活性/碱性染料同浴染色工艺探讨

在用次氯酸钠溶液进行氯漂/氯化的基础上,重点研究了用活性染料/碱性染料同浴对棉盖丙复合针织物染色时,分散剂的用量、碱剂的用量、染色温度、染色时间等因素对染色效果的影响。试验结果表明:当 IW分散剂用量为2．5g/l时可获得比较好的分散效果,弱碱性条件下棉的色差很小,丙纶的色差也可以接受; 温度低时,对碱性染料上染丙纶不利,90℃时染色效果较好,同浴染色时间增加,色差明显增大。     

Studies on indigo dyeing and diffusion by the film roll method

The influence of reducing agent, indigo concentration and dyebath pH on indigo dyeing and diffusion was studied for the film roll method. An almost linear relationship between the indigo concentrations in the dyed film and in the dyebath was maintained throughout the experiments. Two different calculation methods were used to obtain the diffusion coefficient and the surface indigo concentration in the film. Similar surface indigo concentrations were obtained from the two methods, but a lower diffusion coefficient was obtained by the approximate integral method. It was found that the dyebath pH is the dominant factor influencing the rate of diffusion of indigo and the colour yield of the dyed film. The dyebath pH also had a considerable influence on the reduction of indigo to leuco-indigo, a step that is essential to the dyeing process.