Improving the dyeability of wool by treatment with chitosan

A study of pretreatment of wool fabrics with chitosan by a pad-dry method has been carried out. The pretreatment effectively eliminates differences in dyeing behaviour between damaged and undamaged wool fibres, with an increase in the rate of dye uptake and the exhaustion of acid and reactive dyes. Penetration of the fibre by dyes has been followed using fluorescence microscopy and the role of the chitosan coating in the dyeing process clarified. Similar colour fastness properties were obtained on both untreated and chitosan-treated wool fabrics. The chitosan coating on wool fabrics has been examined by scanning electron microscopy. Evidence for the presence of chitosan was sought using a colorimetric method. It is believed that an approximately uniform and adherent chitosan sheath is formed on individual wool fibres.     

A new approach to improve dyeability of nylon 6 fibre using a subtilisin enzyme

This study confirms the structural changes of nylon 6 fibres using protease by measuring the dyeability, hydrophilicity, chemical changes and fastness properties. For this purpose, nylon 6 fabrics were first treated with different concentrations of protease enzyme in aqueous solutions. The dyeing process was then carried out on the treated fabrics with disperse and acid dyes. Acid and disperse dyes showed higher exhaustion on the enzyme‐treated samples. The results of colour measurement in the CIELAB system showed that the darkness of the samples increased with an increase in the enzyme percentage in the solution. The results of moisture regain showed that treatment of nylon fabrics with a proteolytic enzyme caused an increase in moisture absorbency. The wash and light fastness properties of samples were measured according to ISO 105‐C05 and daylight ISO 105‐B01 and are discussed.     

合成纤维及其混纺纤维用染料的研究 Ⅰ.用于锦纶染色的含β-羟乙基砜硫酸酯基活性分散染料

本文综合了应用于锦纶染色的弱酸性染料酸性浴上色的高竭染率,活性染料与纤维的共价键结合,分散染料在纤维上迁移、匀染、盖染性好等优点,提出一类含β-羟乙基砜硫酸酯基的活性分散染料。用分子较小的分散染料结构,以含β-羟乙基砜硫酸酯为活性基;在弱酸性浴中染色,再在弱碱性浴中与聚酰胺纤维反应成共价键结合。 合成了一系列偶氮型和蒽醌型染料。进行了合成工艺、对锦纶的染色性能以及染色锦纶的牢度等试验。并讨论了染料与聚酰胺纤维的结合 这类染料可用于锦纶66和锦纶6丝纺、弹力锦纶丝和针织品,还可用于桑丝、柞丝及其与人造丝的提花织物。这类染料在锦纶上色泽鲜艳,竭染率较高,益染性优良,耐晒、耐湿处理等牢度较好,适于各种锦纶织物的染色。这类活性分散染料,具有酸性染料、活性染料和分散染料染锦纶的主要特点。     

Improving the dyeability of synthetic fabrics with basic dyes using in situ plasma polymerisation of acrylic acid

The in situ polymerisation of acrylic acid using low temperature plasma treatment was carried out on polyester, polyamide and polypropylene fabrics with the aim of improving their dyeability with basic dyes. The overall colour strength obtained was significantly increased as a result of this treatment. However, while the wash fastness was acceptable on polyamide, it was unsatisfactory on polyester and polypropylene fabrics, probably due to lack of penetration of these fibres by the acrylic acid monomer. Scanning electron microscopy and Fourier transform infrared spectroscopy confirmed that grafting of polyacrylic acid had taken place only on the surface of the polyester and polypropylene fibres, but in the case of polyamide the interior of the fibre was also modified.     

Developments in the chemistry of reactive dyes and their application processes

This review describes the immense impact of reactive dyes on the textile industry. Their use on cellulosic fibres is especially important, but their growing popularity on polyamide substrates is notable. Detailed information is given about developments both in the chemistry of reactive systems and in the chemical technology involved in their application to a variety of fibre types. It is also pointed out that further research is necessary to improve dye–fibre fixation efficiency, especially when dyeing full shades on cellulosic fibres. This work is necessary to address the current environmental problem of colour in dyehouse effluent. The potential solutions reviewed include multifunctional reactive dyes, cationic reactive dyes, and cellulose fibre modification.     

One‐bath union dyeing of a modified wool/acrylic blend with acid and reactive dyes

Pretreated wool/acrylic fibre was obtained by a facile amidoximation process. Fibre characterisation (nitrogen content, tensile strength, shrinkage, infrared spectra and X‐ray diffraction) proved the success of the pretreatment. Union dyeing of wool/acrylic fabrics with acid and reactive dyes, namely CI Acid Red 40, CI Acid Blue 25, CI Reactive Red 194 and CI Reactive Blue 25, was obtained using a one‐bath dyeing process. Different factors that may affect the dyeability of the blend fibre, such as dyebath pH, liquor ratio, temperature, time and dye concentration, were evaluated with respect to the dye exhaustion, fixation, colour strength, levelling and fastness properties. Excellent to good fastness was obtained for all samples, irrespective of the dye used. The result of the investigation offers a new viable method for union dyeing of wool/acrylic fibres in a one‐dyebath process.     

The roles of polymer relaxation phenomena,aqueous dye solubility and the physical properties of water in the mechanism of adsorption of a disperse dye on poly(ethylene terephthalate) fibres: Part 4 further aspects related to polymer relaxation phenomena

To further investigate the contribution of polymer relaxation times to the mechanism of disperse dye adsorption on poly(ethylene terephthalate) fibres, the temperature-dependent uptake of Teratop Yellow HL-G 150% on both cotton and polyamide 66 fabrics at temperatures between 30 and 130°C was compared with that on poly(ethylene terephthalate) fabric. Although uptake of the commercial grade dye on polyester fabric is governed by the thermally regulated, broad glass transition of the water-saturated poly(ethylene terephthalate) substrate, as this was not observed for either cotton or nylon 66 fabrics, the respective cellulose or polyamide 66 polymer glass transition does not present a major thermal impediment to dye uptake over the wide range of dyeing temperatures used. This is because the onset and end-set temperatures of the glass transition of the water-plasticised poly(ethylene terephthalate) material reside within the range of dyeing temperatures employed, whereas those of the water-plasticised cotton and polyamide materials occur below the lowest dyeing temperature examined (30°C). The thermal dependency of disperse dye solubility also likely makes a meaningful contribution to the temperature-dependent dye uptake observed for each type of fibre.     

Dyeing behaviour of lyocell fabric: effect of fibrillation

To understand the effect of fibrillation in dyeing, non-fibrillated lyocell fabrics and fibrillated lyocell fabrics were dyed with different types of reactive dyes. Their exhaustion, fixation and K/S values were measured and compared. It was observed that fibrillated lyocell shows lower visual colour yield than non-fibrillated lyocell, independent of the exhaustion and fixation. It was also observed that some bifunctional reactive dyes, because of the location of reactive groups and flexibility of their structure, reduced fibrillation of lyocell through crosslinking. It was shown that defibrillating fibrillated lyocell with a cellulase enzyme increased the visual colour yield. Non-fibrillated lyocell fabrics after dyeing were subjected to a hydroentanglement treatment to create a fibrillation effect. These properties suggest that the lower visual colour yield of fibrillated lyocell is not mainly attributed to any change in fibre properties of the fibrils, but as a result of the light scattering from the fibrillated fabric surface.     

Synthesis and properties of acid dye derivatives of arylsulphonanilides

Thirty-five acid dyes suitable for dyeing wool and polyamide fibres were synthesized, using derivatives of arylsulphonanilides prepared from o-nitrotoluene or chloronitrotoluene. As coupling components, derivatives of 1-phenyl-3-methylpyrazolone-5 and 2-naphthol were used. Fastness and colour properties of the prepared dyes were determined. It was found that some of the prepared dyes on polyamide fibres show batho- and hypso-chromic effects as well as hypo- and hyper-chromic effects during testing of their fastness to washing and to acid and alkaline perspiration. Spectroscopic examinations and determination of pK_a of the sulphonamide and hydroxyl groups of the dyes showed that the observed changes are associated with aggregation or disaggregation of the dyes on fibres or with a change in the azo-hydrazone equilibrium. Some of the prepared dyes are characterized by very good dyeing and fastness properties.     

Study of the removal of a disperse dye stain from a polyester/elastane blend

Polyethylene terephthalate and elastane fabrics were treated with azo disperse dyes in the same dyebath at 130 °C for 0, 30 and 60 min and then reduction cleared. The dyes adsorbed on each fabric were extracted using monochlorobenzene, in order to determine the amount of disperse dye in each of the polyethylene terephthalate and elastane fabrics, as the dyeing time was increased. It was observed that the amount of dye on the polyethylene terephthalate increased, while that on the elastane decreased, as the time at 130 °C increased from 0 to 60 min. After reduction clearing, the partition ratio of disperse dyes between the polyethylene terephthalate and the elastane increased. The dyed polyethylene terephthalate/elastane blend indicated that those dyes, which exhibited high partition ratios (polyethylene terephthalate:elastane), exhibited correspondingly higher wet fastness properties.     

Dye diffusion and the phenomenon of barriness on polyamide fabrics

Dyed polyamide fabrics tend to exhibit barriness, particularly when acid dyes of good wet fastness are used. The causes of this phenomenon have been investigated by studying the diffusion kinetics of the dyeing process. The conditions used in the pretreatment of the yarn have been considered, in particular the effect of mechanical and thermal conditions during thermal pretreatment. It has been demonstrated that barriness is dependent only on the kinetics of diffusion. If drawing is increased, the rate of dye diffusion is reduced, whereas an increase in the texturising temperature tends to increase it. The influence of dye diffusion decreases as the dyeing temperature rises. The traditional practice of dyers to attempt to reduce barriness by raising the dyebath temperature very slowly therefore makes matters worse. To reduce barring it would be preferable to introduce the dyestuff to the dyebath only once the dyeing temperature has been reached.     

Comparison of the effects of various presettings on the colour of polyamide 6.6 dyed with acid dyestuffs

Polymeric fibres are semicrystalline structures in which the macromolecules are rarely oriented in their equilibrium state. Further instabilities are imparted when the fibres are converted to yarns and the yarns to fabrics. Heat-setting is an important industrial process, as it reduces the fibre strain to an acceptable limit. This paper presents results of a study on the effects of various presettings (heat-, steam- and hot water-setting processes) on the dyeing properties of polyamide 6.6 fibres with acid dyestuffs. It was found that the colour yield is lower for dyed samples after dry heat-setting, but in the case of samples that have been hot water-set or steam-set, the colour yield increases slightly for light shades and remains constant for dark shades, compared with the unset dyed sample.     

One‐bath union dyeing of wool/polytrimethylene terephthalate blends†

The one‐bath dyeing of blends of polytrimethylene terephthalate (PTT) staple and wool has been investigated. The exhaustion of selected Terasil disperse dyes on PTT fibre and Lanasol reactive dyes on wool was measured as a function of temperature, together with the cross‐staining of the Terasil dyes on the wool component and the Lanasol dyes on PTT component. Most Terasil disperse dyes achieved satisfactory dye uptake on PTT at 110 °C, whereas on conventional polyester (polyethylene terephthalate) temperatures of up to 130 °C are required. An optimised union‐dyeing technique for wool/PTT blends was developed which minimised the staining of Terasil disperse dyes on wool and produced dyed goods with high levels of wet colour fastness. Carriers were not required to enhance the dyeability of PTT at low temperatures. The wool component appeared to be protected against damage at 110 °C by the reactive dyes. The results indicate the potential for blending PTT fibre and wool to produce fabrics that are easier to dye at lower temperatures than conventional wool/polyester blends.     

Low-temperature dyeing of meta-aramid fabrics pretreated with 2-phenoxyethanol

In this study, meta-aramid fibres were pretreated with 2-phenoxyethanol under different conditions to investigate the effect of 2-phenoxyethanol on the dyeing of aramid at low temperature (95 °C). Structural alteration of the pretreated fibres was reflected by thermogravimetry and Fourier transform infrared spectroscopy, indicating more H-bonds, lower crystallinity, and slightly lower thermal stability. The change in structure showed that 2-phenoxyethanol combined with the fibre macromolecules and resulted in swelling of the fibre. Creation of a biphasic system through the addition of 2-phenoxyethanol to the dyeing solution resulted in the cationic dye being partitioned more towards the 2-phenoxyethanol-rich phase than the aqueous phase. The cross-sections of the dyed fibre suggested that the meta-aramid fibre could be dyed more thoroughly with an appropriate concentration of 2-phenoxyethanol. The colour value of aramid fabric was tested by varying the concentration of 2-phenoxyethanol and the temperature of pretreatment, indicating a dramatic improvement in dyeing performance to aramid after 2-phenoxyethanol pretreatment. 2-Phenoxyethanol pretreatment and low-temperature dyeing can overcome the problems of chemical and energy waste while producing a satisfying colour.     

Recent Developments in the Dyeing of Stretch Materials

At the present time, the preferred method for dyeing nylon-wool stretch fabrics is to use selected acid dyes for both fibres in conjunction with a bifunctional dyebath assistant that allows easy control of levelling as well as of the depth of colour on the two fibres. A product of this type, viz. Erional PW (Gy), is discussed in detail. This new dyeing assistant is also useful when dyeing blends containing elastomeric polyurethane fibres together with nylon or nylon and wool.     

The Development of Dyes and Methods for Dyeing Polyester

Early work on the dyeing of polyester fibre showed that only dyes of very low aqueous solubility had substantivity for the fibre, and that for dyeing at the boil without a carrier only the smallest molecular weight disperse dyes, and selected azoic combinations, had sufficiently high dyeing rate to give adequate colour yield in a practicable time of dyeing. The development of carriers for dyeing at the boil, and of machinery for batchwise dyeing under pressure at temperatues up to 140°C, extended the range of suitable dyes to those of lower dyeing rate but higher heat–fastness properties. As an alternative to exhaust dyeing, polyester may be dyed with disperse dyes by padding followed by dry heat fixation at temperatures up to 220°C, and this method has found its main commercial application in the continuous dyeing of polyester–cellulosic blend fabrics. The development of new disperse dyes has followed these trends in application methods, and the proportion of available dyes having higher heat–fastness properties has steadily increased from about 1950 onwards. Improvements have also taken place over the same period in the physical properties of the dyes, to meet the increasingly severe demands on dispersion properties imposed by the newer dyeing methods.     

Studies on Some New Reactive Disperse Dyes

The preparation of some new reactive disperse dyes which can be used for dyeing 100% synthetic and fibre blends is described. The preparation of some disperse dyes containing a chlorohydrin group is also described. This radical is the precursor of the epoxide reactive group in the active form of these dyes. Dyeings produced on various fibre blends by a two–stage high–temperature and by a carrier–dyeing technique are assessed. It was found that dyeings produced by the high–temperature technique were brighter, more level and possessed much better technical properties than those obtained using the carrier–dyeing method. The fastness properties of dyed samples were determined and found to be comparable with those of conventional disperse and reactive dyes. The colour yield was also determined in order to examine the possibility of obtaining deep dyeings on blended fibres, and to evaluate the potential commercial use of these dyes for dyeing blends as well as 100% synthetic–polymer fibres.     

Effect of chitosan on dyeing of chemical fibres

Treatment with chitosan before dyeing significantly improves the properties of fabrics made of polyester and polyamide fibres: it increases the intensity and fastness of the colors of the fabrics; the capillary and sorption properties of the fabrics are improved due to swelling of the chitosan film on the fibre; the mechanism of dyeing textile materials is significantly altered by not requiring penetration of the dye into the depth of the fabric.     

Synthesis and properties of novel aziridinyl azo dyes from 2-aminothiophenes—Part 2: Application of some disperse dyes to polyester fibres

A series of yellow to greenish-blue aziridinyl azo dyes and their azo precursors containing a thienyl coupling moiety has been applied to conventional polyester fibre as well as microdenier polyester by high temperature exhaust dyeing. Heat transferability of these dyes onto polyester fibre has also been examined, using conventional heat-transfer printing techniques. The relevant dyeing characteristics, heat transferability, build-up, dyeability on microfibre polyester, washfastness and lightfastness are given. These aziridinyl dyes are reactive to polyester fibres under HT dyeing conditions. Fabrics dyed with aziridinyl dyes are more resistant to solvent extraction than those dyed with conventional dyes. Residual liquors showed only a pale colour when fabric dyed with aziridinyl dyes was dissolved and then precipitated, whereas a coloured polyester precipitate was obtained.     

The enhanced cationic dyeability of ultraviolet/ozone‐treated meta‐aramid fabrics

Aramid fabrics were photo‐oxidised by ultraviolet/ozone irradiation. The surface properties of the modified fabrics were characterised by reflectance, attenuated total reflectance, electron spectroscopy for chemical analysis and surface zeta potential. The ultraviolet irradiation caused the oxygen content of the aramid fabric surface to increase, with the appearance of carbonyl and hydroxyl groups, and reduced the surface zeta potential, coupled with improved water wettability. Moreover, the crystalline structure did not change after ultraviolet/ozone treatment according to X‐ray diffraction results. The modified aramid fabrics showed higher affinity to cationic dyes, which may have resulted from the newly introduced electrostatic interaction between cationic dyes and anionic dyeing sites on the photo‐oxidised surface layers. Although colour fastness to both staining and rubbing were good to excellent, colour fastness to shade change was moderate. Furthermore, the ultraviolet/ozone pretreatment and cationic dyeing of aramid fabrics may overcome the loss in the mechanical properties associated with previously recommended dyeing methods for aramid fabrics.