Afterclearing by ozonation: a novel approach for disperse dyeing of polyester

A set of trials has been conducted to examine the efficiency of ozonation afterclearing on poly(ethylene terephthalate) fibres dyed with disperse dyes. The afterclearing process was performed in neutral distilled water at room temperature with 12.8 ± 0.3 mg/min ozone at 400 ml/min ozone gas flow rate. The results indicate that 1 min ozonation time is adequate to achieve wash fastness results comparable with conventional reduction clearing without significant colour yield losses. Ozonation periods greater than 1 min not only caused significant colour yield losses, but also caused a severe decrease of the breaking load of the fabric. The advantages of ozonation afterclearing are: savings in energy and time, as it is performed at room temperature for only 1 min, and decrease of environmental load as it avoids the use of the harsh chemicals used in conventional reduction clearing.     

Practical realisation of ozone clearing after disperse dyeing of polyester

In this study, a novel system utilising ozone in jet dyeing machines is introduced, and the results of ozone‐clearing treatments of disperse dyed polyester on the prototype modified machine are reported. A Venturi injector was mounted on the liquor circulation pipe of the jet dyeing machine to feed ozone gas into the machine. Ozone was generated via an ozone generator by feeding conditioned air into the generator. The ozone gas entering the pipe partly dissolved in the treatment liquor; the dissolved portion and the gaseous ozone interacted via the fabric in the pipe, especially in the nozzle and also at the bottom of the autoclave (machine body). Disperse dyed polyester fabrics of textile‐company mass production were ozone cleared in this prototype. Ozone clearing was achieved in cold water (room temperature), and no other chemicals were used. The colour of the samples, wet fastness properties, and the chemical oxygen demand of the effluent were investigated, and costs were compared with those of conventional reduction clearing of ozone. Results were outstanding: an 83% cost reduction, 67% timesaving, and an 88% COD reduction were achieved.     

Dispersant-free dyeing of polyester with temporarily solubilised disperse dyes

In an effort to overcome some of the environmental problems associated with the use of dispersing agents, four temporarily solubilised disperse dyes had previously been synthesised and characterised for use in dispersant-free polyester dyeing. In this paper the dyeing and fastness characteristics of these dyes on polyester fabrics have been examined. It was found that the optimum pH to guarantee a moderate rate of hydrolysis was 5, which allowed temporarily solubilised disperse dyes to be successfully applied to polyester without the use of dispersants. The dyebath remained stable during the dyeing procedure. The dyes exhibited good levelling and fastness properties on polyester.     

Mechanism and application of ozone fading: Oxidative decolorisation of disperse dyes and waste-dyed polyester fabrics

As the most common synthetic fibre, polyester has consistently been in high demand and usage, but its recycling has always been a problem for the textile industry. The decolorisation of dyed polyester is the key to expanding its recycling use, and there is no rapid, effective and simple decolorisation method. In this study, ozone was used to decolorise dispersed dyes developed for polyester. Ozone was effective in decolorising CI Disperse Orange 30 and CI Disperse Blue 60, and the process was extended to the decolorisation of dyed polyester fabric. Based on single factor analysis, the optimum decolorisation technological conditions were: an ozone feed rate of 130 mg L⁻¹ min⁻¹, treatment time of 2 hours, wet pick-up of 100% and pH value of 3, with which the decolorisation rate and colour difference values could exceed 45% and 6%, respectively. The changes in dye structure during the process of ozone decolorisation were analysed using scanning electron microscopy, X-ray diffraction and Fourier Transform–infrared spectroscopy, and the mechanism of ozone decolorisation was also investigated. The results showed that the crystallinity decreased from 41.18% to 36.30% with a strength retention rate of above 80%, and demonstrated that ozone can be used on polyester fabric and dye simultaneously. The aim of entering the fibre was achieved by etching the polyester and decolorisation was achieved by oxidising the chromaticity groups.     

Improved mechanism of polyester dyeing with disperse dyes in finite dyebath

A new sorption mechanism of polyester dyeing with disperse dyes in water is proposed. It is considered dye aggregates could not be sorbed unless they turn into single molecules. However, this theory could not explain numerous sorption phenomena: sorption continues when equilibrium dye concentration exceeds its solubility; dyeing at long liquor ratio, using microencapsulated or crystal‐modified dyes do not change concentration of single dye molecules or dye solubility, but increase sorption rate and quantity in a fixed time. We demonstrate that both single and aggregated dye molecules could be sorbed using CI Disperse Blue 56. Because of the large size and low diffusion rate, dye aggregates could temporarily block sorption channel and prevent entry of other dyes. Therefore, only using extra more dyes could get a dark colour. Series of approaches could be proposed to reduce or eliminate the sorption problems caused by aggregates using the new sorption mechanism.     

Effect of pH control on dyeing of polyester materials with disperse dyes

Dyeing of polyester materials with disperse dyes at a high temperature in the absence of carriers and at different ranges of dyebath pH was studied. It was found that the behaviour of the dye as well as the magnitude of dye uptake at different pH's are greatly affected by nature and position of the substituents of the dye. Substituents which from lyonium ions in acidic medium produce higher dye uptake in alkaline medium, and those which form lyate ions in alkaline medium bring about higher dye uptake in acidic medium. Substituents which are not able to form neither lyonium ions nor lyate ions yield practically the same dye uptake over a wide range of pH values.     

聚酯超细纤维用分散染料染色性能的研究

该文通过对现有的分散染料染色性能测试,如,聚酯超细纤维的移染性、皂洗牢度及高温分散稳定性等,并进行了碱性染色实验,为选择适用于聚酯超细纤维染色的染料提供一定的参考依据.     

纳米分散染料胶囊的制备及其对涤纶织物轧染染色性能

针对涤纶织物浸轧染色存在浮色多、后水洗负担重的问题，通过乳液聚合法制备了以分散染料为核，甲基丙烯酸甲酯（MMA）-丙烯酸丁酯（BA）共聚物为壳的纳米分散染料胶囊（NDDM），探究了核壳投料比、软硬单体配比、固色温度和固色时间等因素对涤纶织物轧染染色性能的影响。结果表明，NDDM对涤纶织物轧染染色的色牢度和匀染性均优于C.I.分散紫93染色织物，当核壳质量投料比为1:2、MMA和BA质量投料比为1:1，焙烘温度180 ℃、焙烘时间5 min时，NDDM轧染染色织物的颜色深，手感变化小，且未水洗染色织物的各项色牢度达到4级及以上，还原清洗COD值为312.3 mg/L，COD值较C.I.分散紫93染色相比下降了58%。在高温条件下，NDDM内分散染料从聚丙烯酸酯壳层内迁移释放并上染纤维，聚丙烯酸酯壳将未进入纤维内的残余染料覆盖固着在纤维表面。     

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.     

One–bath dyeing of polyester/wool blend with disperse dyes

The present work aims to investigate and develop a one–bath dyeing process for most common blend fibres to replace the conventional two–step process usually applied to dye each fibre constituent separately. The main objectives of the proposed process is the conservation of energy, raw materials, dyes, auxiliaries and labour.     

The effect of dispersing agents on the dyeing of polyester with a disperse dye

An experimental procedure has been devised to study the interdependence of three dispersing agents present in the dyeing of polyester with CI Disperse Orange 21. The method involves the use of ternary diagrams to represent the relationship between dyeing properties and the concentration of dispersing agents present in a dyebath. The technique could be applied to commercial dyeing of polyester with disperse dyes.     

Optimising by response surface methodology the dyeing of polyester with a liposome‐encapsulated disperse dye

Optimisation of conditions for dyeing polyester with liposome‐encapsulated CI Disperse Red 50 was performed using response surface methodology. The effects of temperature, time, and lecithin:dye ratio on the colour strength of dyed fabrics were investigated by a central composite design. The coefficient of determination, the probability value in analysis of variance, and the normality plot of residuals demonstrated sufficient significance of the proposed fitness function. It was found that the temperature and time of the dyeing cycle were effective factors in the dyeing of polyester fabrics with encapsulated dye. It was also established that the colour yield of dyed fabrics was above 25 in the case of a dyeing time of >80 min, a lecithin:dye ratio of ≤2, and a temperature of ca. 128 °C. Comparison of colour strengths produced by liposome‐encapsulated dye and commercial dye revealed that there was approximately the same build‐up on polyester. Dyeings from encapsulated CI Disperse Red 50 exhibited very similar fastness to dyeings from conventional CI Disperse Red 50.     

Effects of the phenol on the dyeing of polyester fibre with some disperse azo-dyes

The effects of the phenol, as carrier, on the dyeing rates, apparent diffusion coefficients, solubilities, thermodynamic affinities and T_D values of some disperse azo-dyes on polyester fibre are reported.The dyeing rates of less soluble dyes are higher than those of more soluble hydrophilic dyes, while the affinity and T_D values show a reversed behaviour.The carrier efficiency on the dyeing parameters studied appears to be correlated with the structure of dyes.     

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.     

Nanofiltration and ozonation for decolorisation and salt recovery from reactive dyebath

Three commercially available high exhaust dyes were used to prepare dyebaths of different shades and subjected to nanofiltration and ozonation. Colour removal, chemical oxygen demand reduction, permeate flux, ozone consumption and total organic carbon removal were analysed to determine the efficiency of nanofiltration and ozonation. It was found that both nanofiltration and ozonation showed a high degree of (>90%) decolorising efficiency. High total organic carbon removal (80%) could be achieved by nanofiltration while ozonation could achieve only a maximum of 55% total organic carbon removal. The treated dyebath was reused for dyeing the fabric and the fabric quality was compared for the different shades. It was found that the quality of the dyed fabric was good for all shades dyed with nanofiltration permeate. The quality of the dyed fabric was affected for dark shades dyed with the ozone decolorised dyebath.     

The dyeing and colour characteristics of alkali–treated polyester fibres dyed with disperse dyes

Alkali–treated and untreated polyester fabrics were dyed for up to 6 h at 100°C with a series of six disperse dyes of different chemical structures. The alkali–treated polyester samples adsorbed more dye and were dyed to deeper depths of shade and slightly different shades than was the untreated polyester. The greatest differences were observed for the alkali–treated polyester with the most outer surface or skin removed. Dye structure and molecular size also affected the amount of dye adsorbed on the fibres, but did not delineate the nature of differences between skin and core morphology. This study shows that significant differences exist between the molecular structure of the skin and core of melt–spun polyester fibres.     

Carrier‐free dyeing of radiation‐grafted polyester fabrics with disperse dyes

Carrier‐free dyeing of radiation‐grafted polyester fabrics with disperse red dye was studied in the temperature range 283–363 K. 1‐vinyl 2‐pyrrolidone (NVP), acrylic acid (AA) or their mixture was used to graft poly(ethylene terephthalate) (PET) fabric. The effects of pH of the dye solution, graft yield (GY), dyeing time (t), dye concentration (C), and dyeing temperature (T) on the colour difference (CD) of PET fabric were studied. The best dyeing condition was achieved at pH 5.5. CD increases linearly with the increase in GY, with slopes depending on the type of grafted copolymer. CD increased rapidly as the dyeing time increased; this was followed by a relatively slow dyeing rate within a few minutes. The initial dyeing rate (R) was found to increase with an increase in C and T. The dyeing rates for all grafted samples followed 0.35‐order kinetics and are temperature‐independent. Average activation energy 9.26 kJ mol^?1 is calculated for the dyeing process and is independent of the fabric treatment. Pre‐exponential rate constants 1976, 1839, and 1579 (CD/GY) s^?1 were calculated for dyeing PET samples grafted with AA/NVP mixture, NVP and AA, respectively, while 1074 CD s^?1 was evaluated for carrier dyeing of ungrafted fabric. Analysis of the kinetic parameters and the dyeing mechanism revealed that dyeing PET fabric was diffusion‐controlled. Grafting PET fabric improved significantly the dyeing affinity of the DR dye over ungrafted samples dyed in solutions containing a carrier. Copyright © 2005 Society of Chemical Industry     

Neutral dyeing of wool and wool/polyester blend fabrics using sulphatoethylsulphone reactive‐disperse dyes

Two models of temporarily anionic sulphatoethylsulphone reactive disperse dyes were applied to wool, polyester and wool/polyester blend fabrics at different dyeing pH. Maximum exhaustion values and colour yield were observed at pH 7. The results showed that reactive disperse dyes containing bis‐sulphatoethylsulphone reactive groups were more convenient for neutral dyeing of wool and wool/polyester blend fabrics if compared with a dye containing a mono‐sulphatoethylsulphone group. Excellent to very good wet fastness properties on all dyed fabrics were achieved.     

Mathematical relationship between the colour shade depth and the fibre count for disperse dyeing of polyester fibres

The colour shade depth of dyed microfibres is lighter than that of dyed conventional fibres even if there is no difference between the absorbed dye quantities ( M _t) within the fibre. This difference is due to the different light reflectance on the fibre surface for microfibre and conventional fibre, which have a different specific surface area. In this study, the simple mathematical relationship between the colour shade depth, the fibre counts (0.22, 0.56 and 1.46 dtex) and the adsorbed dye quantity is developed for disperse dyeing. The experimental dyeing results and the obtained dyeing results from the simple mathematical relationship were compared for different fibre counts.