Dyeing and fastness properties of phthalimide‐based alkali‐clearable azo disperse dyes on poly(ethylene terephthalate)

The properties of a series of phthalimide‐containing azo disperse dyes and azo dyes with N‐methyl phthalimide moieties in their diazo component were investigated and compared when used to colour polyethylene terephthalate. The N‐substitution of the phthalimide gave a hypsochromic effect on the colour change and better colour yields on poly(ethylene terephthalate) fabrics, probably because of the electron‐donating property of the methyl group and the higher hydrophobicity of phthalimide‐containing azo dyes compared with those containing phthalimide moieties. The results show that phthalimide‐based azo disperse dyes have excellent dyeing fastness properties and that high wash fastness can be achieved using alkali clearance. This alternative clearance method is important for reducing the environmental impact of the dyeing process by replacing reductive clearing and, in particular, by removing the need for sodium hydrosulphite, which creates a high biological oxygen demand when released in conventional disperse dyeing effluent and which generates aromatic amines.     

Dyestuffs for synthetic polymer fibres: 4-N-morpholinoazobenzenes

A series of monoazo disperse dyes derived from the coupling to N-phenylmorpholine of diazotised anilines and aminothiazole derivatives is described. The colour, dyeing and fastness properties of the dyes is compared to those of the analogous dyes based on N-ethyl-N-β-hydroxy-ethylaniline. Dyes from the ring closed heterocyclic coupling components dye synthetic-polymer fibres in deep colours of good fastness properties and show significant hypsochromic colour shifts compared to the uncyclised derivatives.     

Extraction of polyphenolic dyes from henna,pomegranate rind,and Pterocarya fraxinifolia for nylon 6 dyeing

Acid and disperse dyes are two well‐known synthetic materials that are primarily used for dyeing of nylon 6 fibres. Despite their good performance, several negative impacts on the environment, including air and water pollution, are major concerns to researchers. An alternative ecofriendly approach to the dyeing of nylon 6 is the use of natural dyes, given their abundant natural sources, biocompatibility, biodegradability, non‐toxicity, non‐allergic responses, and non‐carcinogenic effects on human life. Based on these advantages, we extracted polyphenolic dyes from henna leaves, pomegranate rind, and Pterocarya fraxinifolia leaves and studied the dyeability on nylon 6 fabric using three compounds of aluminium sulfate, tannic acid, and tin chloride as toxic and non‐toxic mordants before dyeing. Fourier transform infrared spectra of the nylon 6 fabric confirmed the coordination complexes and π–π bonding between the mordants and the dyes. Colorimetric and fastness results showed that the mordants increased the colour strength and improved the fastness properties of the fibres. Our results suggest that tin chloride and aluminium sulfate as metal mordants can be successfully replaced with tannic acid as a biomordant in the natural dyeing of nylon 6. Also, cost assay showed that dyeing of nylon 6 with extracted natural dyes from waste leaves could be a sustainable and economical substitute for synthetic dyeing.     

Pretreatment of cotton fabrics with polyamino carboxylic acids for salt‐free dyeing of cotton with reactive dyes

In this study, polyamino carboxylic acids have been used to improve the dyeability of cotton in a salt‐free reactive dyeing process. These polyamino carboxylic acids were prepared by partial carboxylation of polyvinylamine. Cotton fabric was pretreated with polyamino carboxylic acids and dyed with reactive dyes. The colour strengths of the dyed fabrics were evaluated by measuring the K/S values. The fastness properties (washing, rubbing and light fastness) of the dyed cotton fabrics were also measured. The pretreatment of cotton with polyamino carboxylic acids creates positive charges on the fabric surface. In this way, salt‐free reactive dyeing of cotton or dyeing with only a small amount of electrolyte is possible.     

The effect of polyhydroxyurethane on dyeing of cellulosic fabrics with direct and reactive dyes

Dye yields and fastness properties are reported for direct and reactive dyes using a modified dyeing solution with polyhydroxyurethane. Excellent dye yields and colour fastness properties were obtained without the use of electrolytes, multiple rinsing or fixation agents, which are normally employed in cotton dyeing. From the results, it was found that polyhydroxyurethane media exhibit better dyeability and fastness than the normal aqueous media. Dye adsorption in polyhydroxyurethane media was much higher than in other aqueous systems. The dyed samples showed good hot pressing and washing colour fastness properties within the color change range. The excellent solubility of these dyes in the polyhydroxyurethane aqueous solution makes them ideal for use in exhaustion dyeing.     

Novel hydrolysable azo disperse dyes based on N‐ester‐1,8‐naphthalimide: dyeing of polyester–cotton blends

The dyeing of polyester–cotton blends with new alkali‐hydrolysable azo disperse dyes based on N‐ester‐1,8‐naphthalimide was investigated. Polyester–cotton blend fabrics were dyed using both one‐ and two‐bath methods. Dyes 3 and 4 offered lower colour yield on polyester using the one‐bath method. For the rest of the dyes, employing either the one‐ or two‐bath method resulted in a similar colour yield on polyester fabric. The results for fastness properties and colour yield of the dyeings showed that the dyes were suitable for dyeing polyester–cotton blends using the one‐bath method. The kinetic study of hydrolysis of the dyes in alkali media obeyed the pseudo first‐order reaction rate.     

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.     

A facile synthesis and tautomeric structure of novel 4‐arylhydrazono‐3‐(2‐hydroxyphenyl)‐2‐pyrazolin‐5‐ones and their application as disperse dyes

The main target of this paper was the synthesis of novel azo disperse dyes with better dyeing properties, together with a systematic investigation to determine their dominant tautomer(s) from 12 possible tautomeric structures. In this regard, novel azopyrazolin‐5‐one dyes were synthesised via the reaction of hydrazine hydrate with 2,3,4‐chromantrione‐3‐arylhydrazones. The acid dissociation constants both in the ground and in the excited state for the series prepared were determined and correlated by the Hammett equation. The results of this correlation, together with spectral data, indicated that the compounds under scrutiny exist predominantly in the keto‐hydrazo structure as a Z‐configuration, both in the ground and in the excited state. Finally, the synthesised dyes were applied as disperse dyes for dyeing polyester fabrics, and their fastness properties were evaluated. Also, the position of colour in CIELAB coordinates was estimated and discussed.     

Synthesis,spectral properties and dyeing on polyester of monoazo dyes from indol‐2‐one derivatives

Three series of phenylazo disperse dyes were prepared by coupling diazotised 4‐aniline dyes with 5‐indol‐2‐one dyes. The structures of these dyes were determined by proton nuclear magnetic resonance, Fourier Transform–infrared and elemental analysis. The effects of solvent on the ultraviolet–visible absorption spectra of these dyes were studied. The dyes displayed a λ_max shift of between 399 and 438 nm. The dyes were finally applied in the dyeing of polyester fibres in order to investigate their colour range and dyeing properties. Most of the dyes displayed high rubbing fastness and good washing and sublimation fastnesses on polyester fibres.     

Synthesis of methine dyes derived from indol‐2‐ones and their dyeability on polyester fibres

Three series of methine dyes were synthesised by the condensation of indol‐2‐ones with aryl acroleins. The structures of these dyes were confirmed by ¹H nuclear magnetic resonance spectroscopy, infrared spectrometry and elemental analysis. The ultraviolet‐visible absorption spectra of the dyes were examined in different solvents. The maximum absorption wavelength ranged from 386 to 495 nm. The dyes were applied to polyester fibres, and the colour gamut and dyeing properties were investigated. Results showed that the dye uptake (percentage exhaustion) was 86.9–92.0%, with the hue changing from yellow to red. The rubbing fastness, wash fastness, and sublimation fastness were between 4 and 5.     

Polymerizable Dyes Part II

Abstract

Arylene bisazo resorcinol dyes IIIa-e were prepared and polycondensed with formaldehyde in the presence of aqueous oxalic acid. The resulting polymeric dyes IVa-e were characterized by yield, melting point, colour, elemental analysis and visible and IR spectroscopy. The thermal properties of polymeric dyes were examined by thermogravimetric analysis. Their dyeing performance on nylon and polyester was assessed. The dyeing on nylon and polyester had yellow, orange, red and brown shades with moderate to good, light and wash fastness. Polymerization of bisazo dyes IIIa-e with formaldehyde on dyed nylon and polyester have also been carried out. The dyeing properties of polymeric dyes were compared with the dyes polymerized on nylon and polyester.     

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.     

Enhancing the wash fastness of disperse dyes on wool with oxidants

Disperse dyes are not currently applied to wool commercially, in large part because of inadequate wash fastness, but they do have potential, especially for wool‐polyester blends. In this study, for the first time hydrogen peroxide was investigated to increase the wash fastness of disperse dyes on wool. In the absence of oxidants, 10 disperse dyes from seven classes imparted colours with a range of depths (K/S 2‐26) with wash fastness (grey scale ratings for colour change) grades of 3 to 4‐5. Hydrogen peroxide had only small effects on colours and gave only small enhancements to wash fastness, which were limited to anthraquinone, nitrodiphenylamine, disazo and coumarin dyes. The bleach activators Prestogen W and citric acid enhanced the bleaching effect of hydrogen peroxide but did not assist with raising wash fastness. Hydrogen peroxide in post‐dyeing scouring made the dyeings brighter but did not significantly enhance wash fastness. Ammonium persulphate, which was included for benchmarking with earlier studies, yellowed the wool and decomposed some dyes. This study extends the range of dye classes whose wash fastness on wool can be improved by ammonium persulphate to now include diazo, coumarin and methine, and confirms that oxidants/free radical initiators have potential for enabling the disperse dyeing of wool.     

Reactive dyeing of silk using commercial acid dyes based on a three‐component Mannich‐type reaction

Acid dyes are employed for commercially dyeing silk, which results in ionic bonds between the silk fibroin and the dye. This generally leads to low wet fastness properties for dyed silk fabrics. In this work, three commercial acid dyes with aromatic primary amine structures were selected to dye silk using a Mannich‐type reaction, resulting in improved wet fastness of dyed silk by forming covalent bonds between silk fibroin and dye. The Mannich‐type reactive dyeing was applied to silk fabrics at both 30 and 90°C in trials. Dyeing at 90°C can shorten the dyeing time compared with dyeing at 30°C, even although dye exhaustion and relative fixation at 90°C were a little lower. The dyeing process was optimised when the dyeing temperature was 90°C, dyebath pH 4, dye‐to‐formaldehyde ratio 1:30 and holding dyeing time 60 minutes. The results showed that the dye exhaustion on silk fabrics for the three aromatic primary amine‐containing acid dyes exceeded 94% and their relative fixation was over 80%. Their washing and rubbing fastness reached grade 4 or higher. Hence, the colour fastness properties of dyed silk fabrics using the Mannich‐type reactive dyeing method is superior to the conventional acid dyeing method using the same aromatic primary amine‐containing acid dyes. The Mannich‐type reactive dyeing for silk fabrics at 90°C can be developed into a novel and rapid reactive dyeing method, promising an effective dyeing process with excellent colour fastness.     

Dyeing treatments for protecting colour and colour fastness of green bamboo culms

The effects of various dyestuffs and treatment conditions on the epidermis colour of ma bamboo (Dendrocalamus latiflorus), moso bamboo (Phyllostachys pubescens), and makino bamboo (P. makinoi) were examined to determine the most appropriate dyeing material and approach for endowing bamboo culms with a fascinating green colour without removal of their epidermis. Experimental results revealed that excellent green colour was obtained when the three species of bamboo culms were treated with 0.25% basic dyes in an 80 °C water bath for 30 min (a* values of −19.6, −15.4, and −16.0, respectively). Moreover, alkali pretreatment, though contributing to dyeing effectiveness, yielded bamboo culms with dim surface lightness of low L* values. Dye makino bamboo culms without colour fixation post-treatment changed from green to light green after indoor exposure for 1 year, exhibiting unstable indoor colour fastness. In contrast, colour fixation post-treatment was found to improve colour fastness of bamboo culms; in particular, treatment with 1% glacial acetic acid or 3% tannic acid achieved more uniform dyeing effectiveness and better indoor fastness. By inhibiting discoloration, the natural beauty of bamboo culm can be preserved and its service life can be extended.     

Solvent-assisted Dyeing of Nylon 6.6 and Polyester Fibres

The results of laboratory semi-bulk and bulk trial work on the dyeing of nylon 6.6, with anionic dyes in the presence of n-butanol, in an aqueous dyebath are described. The method gives improvements in coverage of barre which cannot be achieved in other ways, without detectable adverse effects on the physical properties of the nylon 6.6 or the colour and fastness properties of the dyes. Results of work by a similar, solvent-assisted dyeing method for polyester fibre are given. Improvements in migration and speed of fixation of dye in the presence of n-butanol are noted, but these are similar in magnitude to the improvements obtainable with conventional carriers for polyester dyeing at much lower concentrations. The method is likely to be commercially viable only if a substantial proportion of the butanol added to the dyebath can be recovered for re-use. This should theoretically be possible, but experimental confirmation of the process has not yet been obtained.     

Pomegranate fallen leaves as a source of natural dye for mordant-free dyeing of wool

The application of metal mordants is usually necessary in dyeing of wool with natural dyes to improve the dye exhaustion and fastness properties. The majority of metal salts generally used as mordants are considered as toxic and it is important to find replacements for them. Plant sources with high content of tannins are good candidates as bio-mordant or colourant to overcome this drawback. In this study, the waste fallen leaves of pomegranate tree were used as a source of natural dye for the eco-friendly dyeing of wool fabric without the use of metal mordants. The dyeing process variables including dye concentration, dyebath pH, and temperature were optimised using response surface methodology to obtain the highest colour strength. The colour strength was increased by increasing the natural dye powder up to 100%owf while the optimum pH and dyebath temperature were 4 and 100°C, respectively. The sample dyed under the optimal condition exhibited good fastness properties against washing and light. This study approved the potential of Punica granatum fallen leaves for the dyeing of wool without any mordant, while high fastness properties were obtained.     

Evaluation of antimicrobial and dyeing properties of walnut (Juglans regia L.) green husk extract for cosmetics

Walnut green husk is one of the main waste products from walnut and could be used as a source of natural dyeing compounds such as juglone. The present study was conducted to evaluate the effective use of walnut green husk extract as a natural hair dye. Dyeing properties, fastness and antimicrobial behaviours of dyed hair and also a skin irritation test for natural hair dye on rat skin were examined. When the extract was mixed with ascorbic acid as a developer, ferrous sulphate as a mordant, and Aloe vera extract used as a secondary mordant and also a cosmetic ingredient, the reaction resulted in a dark‐brown colour on hair samples. The dyed hair exhibited appropriate colour strength having excellent morphology for a hair surface coated with dye molecules. In addition, the dyed hair possessed good resistance to washing and daylight fastness, without any irritant properties as shown in a rat model, although high concentrations of iron‐based mordant may be problematic for long‐term usage. This paper also suggests the use of natural mordants such as lactic and oxalic acids to avoid any probable risks. Walnut green husk extract was an appropriate natural hair dyeing agent in practice and showed maximum antimicrobial activity compared with semi‐synthetic and commercial hair dyes. The results demonstrated that walnut green husk can be used as an economical, valuable, eco‐friendly and safe source of dyeing and antimicrobial agents for cosmetic products.     

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.