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.     

Dyeing of wool with temporarily solubilised disperse dyes

Temporarily solubilised disperse dyes derived from aminophenyl-4-(β-sulphatoethylsulphone) have been applied to wool fabric without the use of a levelling agent. By virtue of their characteristic dye structure, excellent levelling properties were observed on wool fabric. Good exhaustion, fixation and fastness test values were also obtained.     

The rate of hydrolysis of temporarily solubilised disperse dyes

Four temporarily solubilised disperse dyes were synthesised. To obtain the optimum application conditions for dispersant-free polyester dyeing, their conversion rates into insoluble derivatives were measured using HPLC and found to be more dependent on pH than on temperature. The results showed that it was possible to use these dyes in dispersant-free polyester dyeing for which the optimum application pH was between pH 5 and 6 at which the hydrolysis rate of the dyes was moderate.     

Dispersant-free dyeing of polyester with temporarily solubilised azo disperse dyes from 1-substituted-2-hydroxypyrid-6-one derivatives

Four temporarily solubilised azo disperse dyes based on 1-substituted-2-hydroxypyrid-6-one were synthesised and characterised. The dyes showed high extinction coefficients and had a yellow shade on polyester fabric. They were successfully applied to polyester without the use of dispersants and the optimum pH was found to be 5. It was found that the dyes could be alkali-cleared due to ionisation of the dye under mild alkaline conditions. The dyes exhibited good to excellent fastness properties on the polyester fabric.     

Dispersant‐free dyeing of poly(lactic acid) fabric with temporarily solubilised disperse dyes from azopyridone derivatives

Poly(lactic acid) fibre is derived from annually renewable crops and known to be 100% compostable. In order to extend its environmental friendliness into the dyeing process, dispersant‐free dyeing of poly(lactic acid) fabric with three temporarily solubilised azo disperse dyes based on hydroxypyridone moiety containing a β‐sulphatoethylsulphonyl group was investigated. The dyes were successfully applied to poly(lactic acid) fabric without the use of dispersants. The colour yields of the dyes on poly(lactic acid) fabric were observed to be dependent on dyebath pH and dyeing temperature. The optimum results were obtained at pH 4–5 and 110 °C. One of the dyes showed a colour yield as good as that of a commercial disperse dye and good build‐up on poly(lactic acid) fabric. All of the dyes could be alkali cleared owing to ionisation of the dye under mild alkaline conditions. Wash fastness was good to very good, and light fastness was good. The chemical oxygen demand levels of the poly(lactic acid) dyeing effluent from the dyes were considerably lower than those from a commercial disperse dye.     

Afterclearing of disperse dyed polyester with gaseous ozone

The efficiency of ozone treatment for the clearing of disperse dyed polyethylene terephthalate fibres has been examined. The ozone treatment for the clearing of the dyed samples was performed by blowing the ozone gas from the ozone generator on to the wet fabric samples. The results indicated that 3‐ and 5‐min ozonation times were appropriate to achieve comparable wash fastness results with conventional reduction clearing without significant colour differences (ΔE* value) for the samples dyed with CI Disperse Yellow 23 and CI Disperse Blue 79, respectively; however, the ozonation time had to be increased to 15 min for CI Disperse Red 82. Tensile strength tests and scanning electron microscopy analysis indicated that the ozone treatment did not cause any severe damage to the fabrics. Ozone treatment for the afterclearing of disperse dyed polyester fabric can lead to energy and time savings and environmental load reduction when compared with conventional reduction clearing. This study tested a new method of ozone application for clearing of disperse dyed polyester by blowing ozone directly on to the fabric samples. This new method of application has the advantage of being readily adoptable for continuous treatment lines and lower water consumption.     

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.     

Halochromism of acrylic fibres dyed with some disperse dyes

Anomalous dyeing behaviour has been found when regular acrylic fibre treated in hydrochloric acid, in which the sulphonic acid group was present entirely in the acid form, was dyed in neutral condition with azo and anthraquinone disperse dyes. In the very early stages of dyeing there was an abnormally high degree of dye exhaustion, with bathochromic (azo) or hypsochromic (anthraquinone) colour changes on the fibre. These phenomena gradually disappeared after prolonged dyeing, with normal adsorption equilibria and colours eventually being obtained. The results were explained on the basis of protonation by the sulphonic acid groups of treated fibre which occurs at the azo nitrogen or the amino nitrogens of the substituents in the 1 — or 1,4-positions of anthraquinone. The normal adsorption equilibria after prolonged dyeing was attributed to hydrolysis of the cyano side group to form carboxylic acid. This produces ammonia to liberate neutral dye from the protonated dye cation adsorbed electrostatically by the sulphonic acid anion of the treated fibre.     

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。     

Synthesis of temporarily solubilised azo disperse dyes containing a β‐sulphatoethylsulphonyl group and dispersant‐free dyeing of polyethylene terephthalate fabric

Disperse dyes containing a β‐sulphatoethylsulphonyl group have temporary solubility and can be applied for dispersant‐free dyeing of hydrophobic fibre. Six novel temporarily solubilised azo disperse dyes having a β‐sulphatoethylsulphonyl group in their structures were synthesised, and their dyeing properties on polyester were investigated. As a dye intermediate, a diazo component having dibromo groups was prepared, and 4‐diethylamino‐4′‐(2‐sulphatoethylsulphonyl‐4,6‐dibromo)azobenzene dyes were prepared by a diazo‐coupling reaction. Then, the dyes containing dicyano groups were prepared by cyanation of corresponding dyes with dibromo groups. The absorption maxima of the dyes were affected by the substituents in the diazo and coupling component rings and varied from 434 to 616 nm in dimethylformamide. Polyethylene terephthalate woven fabric could be dyed with the synthesised temporarily solubilised dyes without using any dispersants. Dyebath pH affected the K/S value at maximum absorption as well as percentage exhaustion on polyethylene terephthalate fabric, and the optimum pH was 5. The dyes gave brownish orange, red, purple, and greenish blue hues on polyethylene terephthalate fabrics, and colour build‐up was good. Wash fastness was good to excellent, rubbing fastness was moderate to excellent, and light fastness was poor to moderate.     

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.     

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.     

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.     

Cationic organofluorosilicone as deepening agent in the application of dyed polyester fabric

Polyester fabrics are usually difficult in dyeing deeply due to their dense structure and high surface refractive index, and deepening finishing is an effective method to obtain dark polyester fabrics. In this article, octamethyl cyclotetrasiloxane (D₄), 1,3,5-tris(3,3,3-trifluoropropyl)-methylcyclotrisiloxane (D₃F), and silane coupling agent KH-902 were used as main monomers to synthesize organic fluorosilicone, and further to prepare cationic organofluorosilicone (COFS) and COFS darkening agent. FTIR and ¹H-NMR were used to characterize the structure of synthetic products. The finishing experiments confirmed that COFS darkening agent had good shade darkening on dyed polyester fabrics with small color change. The optimum conditions of deepening finishing were COFS darkening agent concentration of 20%, the pick-up of 85%, and the curing temperature of 180 °C. After finishing, the dyed fabric had no lowering effect on color fastness, all at grade 4 or above. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48208.     

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.     

Prediction of depth of shade of a dyed polyester fabric based on fibre fineness and fabric structure

A colour prediction model containing four parameters of dye concentration, fibre fineness, fabric roughness and dye parameter is developed. The model can predict the shade depth of a dyed polyester fabric. The relationship among these factors and shade depths of dyed polyester fabrics was investigated to elucidate the role of fibre fineness and fabric structure on surface reflectance and colour efficiency. The shades of several additional dyed samples were measured and compared against the predicated values to validate the accuracy and performance of the model. The results showed that the predicated depths of shade matched the experimental data to a good extent.     

Dyeing of polyester using micro-encapsulated disperse dyes in the absence of auxiliaries

Polyurea microcapsules were prepared in this study, using disperse dye as the core material and diphenylmethane-4,4'-diisocyanate as the wall-former. Microencapsulated disperse dyes have been characterised in terms of their thermal properties, average particle size and size distribution, morphological structure and composition. Polyester fabric was dyed with microencapsulated CI Disperse Blue 56 using a high temperature dyeing process without dispersing agents, penetrating agents, levelling agents or other auxiliaries. The quality of the polyester fabric dyed in this manner – without reduction clearing – was at least as good as that dyed traditionally after washing and reduction clearing. After separating off the polyurea microcapsules, the dyebath was virtually colourless and was shown to be suitable for reuse.     

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.     

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.