Organoclays assisted vat and disperse dyeing of poly(ethylene terephthalate) nanocomposite fabrics via melt spinning

Polyethylene terephthalate nanocomposites containing six modified montmorillonite nanoclays were prepared by a melt compounding technique. The effect of intercalated compounds of montmorillonite on textile mechanical properties of resultant polyethylene terephthalate nanocomposite fabrics was investigated. Winding was not possible, when the polymers were first compounded with the desired amount of montmorillonite and then spun, as filament breakage occurred. Spinable polymer were only obtained by mixing polyethylene terephthalate master batches with 4 wt% montmorillonite, which contained tallow intercalating compound with pure untreated polyethylene terephthalate to a montmorillonite content of 0.5 wt%, thus decreasing the concentration of thermally degraded polymer chains. After spinning the fibres were drawn and knitted into fabric samples for further testing. The prepared polyethylene terephthalate nanocomposite fabrics using montmorillonite exhibited higher colour strength using vat and disperse dyes compared with those of the reference fabrics made from fibres spun without montmorillonite clay content and regular fabrics. The carbocyclic‐based vat dyes have higher colour strength values on polyethylene terephthalate nanocomposite fabrics if compared with heterocyclic‐based vat dyes. The colour fastness ratings for both vat and disperse dyeings secured very good to excellent washing and perspiration fastness on polyethylene terephthalate nanocomposite fabrics. All dyed fabrics showed excellent light fastness using vat and disperse dyes. The preparation of polyethylene terephthalate nanocomposite fabrics with improved textile mechanical and vat dyeing properties needs further investigations.     

Fluorescence and kubelka-munk theory

An expression is derived for the spectral radiance factor of a thick sample of material which scatters and absorbs light, and to which has been added a fluorescent dye. It is also shown how to work backwards, calculating absorption and emission spectra of the dye from measurements on dyed and undyed samples. This theory has practical application in colorant formulation, and examples using up to three dyes to colour paper are discussed.     

粘胶纺液着色用还原染料两元拼染中性色的研究

中性色具有特殊的色彩魅力,深受人们的喜爱.但是,因为中性色多为三次色,所以在印染加工中存在拼染困难、成品色光稳定性差等缺点,这对粘胶纺液着色加工,会产生致命的影响.本文选取8种还原染料,对以"两元拼色"方式拼染中性色的可行性进行了研究.实验表明,以"两元拼色"方式,基本可以实现对中性色的色调、饱和度和明度的覆盖."两元拼色"有利于提高中性色的拼染效率和成品色光的稳定性.     

Colour constancy of vat prints on cotton fabrics

Colour constancy of prints with vat dyes on cotton fabrics was investigated by computing the CMCCON02 colour inconstancy index with the key element CAT02 for chromatic adaptation transform. The results show that the highest changes in colour appearance can be expected when the average daylight is replaced with fluorescent light. If D65 daylight is replaced with some other type of daylight, such as D50 or D55, only minor colour deviations occur which do not substantially change the colour appearance of the prints. The analysis of the influence of the lightness and chromaticity of prints shows that the chromaticity of the samples significantly affects their colour constancy. The change of appearance of the prints with lower chroma because of changed illumination conditions is less probable. The influence of a dye blend composition was also investigated. On average, multi‐coloured dye blends have proved to be more colour constant.     

Dyeing of polyester and its blends with some disazo dyes derived from the disodium salt of chromotropic acid and their chelates with transition metal ions

Disazo dyes derived from the disodium salt of chromotropic acid and their chelates with metal ions were applied on polyester, polyester/cotton and polyester/wool blend fibres as disperse dyes. The fastness to washing, perspiration, rubbing and light of the resultant dyeings were measured. The bonding of dye or its complexes to the fibre and the effect of substituent groups on the colour fastness of the dyes are discussed.     

Decolorising textile effluents

Amendments to the legislation on waste water are making the legal requirements for textile waste water more stringent. In addition to the limits on the metal content and the COD and AOX values, restrictions are also being placed on the colour of the effluent. Anionic dyes (e.g. reactive dyes and metal-complex acid dyes) are removed from spent dye liquors by means of ion pair extraction by long-chain amines. The effect of pH and the structure of the amine has been studied. In reactive dyeing such treatment reduces both the amount of colour and the AOX value. In the case of the metal-complex dyes the removal of the (chelated) metal is of prime importance. The metal-complex dyes can be recovered from the organic phase by extraction with caustic soda and then re-employed in dyeing. The amines that result at the end of dye recovery are practically colourless and may be reused.     

Instrumental Colour Prediction A Potential Aid to Dye and Process Selection

A relationship has been established between the dyeing properties of fibre–reactive dyes and the spectral reflectance properties of the colours produced on machine–washable wool. The information gained in routine dye calibration for instrumental colour–prediction systems may be used by the practical dyer for dye selection. The spectral reflectance properties of the resultant dyeings are explained in terms of the diffusion, fixation and level–dyeing properties of specific fibre–reactive dyes applied to wool by exhaust and pad–dyeing processes.     

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).     

Evidence for the Participation of Singlet Oxygen in the Vat–dye Photosensitized Degradation of Cellulose

A study has been made of the vat–dye photosensitized degradation of cellulose. Whilst the part played by the dyes in direct hydrogen abstraction from a cellulose substrate cannot be overlooked, it is apparent that the role played by singlet oxygen is important. The ability of a dye to produce singlet oxygen has been studied by measuring the amount of tetraphenylcyclopentadienone the dye can photo–oxidize. It would appear that the singlet oxygen is initially formed in its high energy g state by energy transfer from the triplet state of the dye to ground state molecular oxygen. Luminescence spectroscopy has been employed in order to gain information about the excited state energies of the dye molecules, and an electron spin resonance study of the dyes in rigid media has been carried out in order to obtain information about the triplet state.     

Substantivity of anthraquinone vat dyes

The microcrystalline aggregates model of the adsorption of vat dyes on cellulosic materials is substantiated in this study. The relationships between affinities of some anthraquinone vat dye models and van der Waals molecular areas, hydrophobicity and planar-like structures are presented in the form of correlation equations.     

Colorant formulation based on new two-constant theory

A new two-constant theory for colour matching has been developed based on the Kubelka–Munk theory. Colorant formulations and algorithms for matching tristimulus, K / S and reflectance values of a standard are presented based on the new theory. The algorithms are suitable for a single-constant theory as well as a two-constant theory. The experimental data show that the recipes predicted by the new two-constant theory are closer to the actual recipes of the standard sample than the recipes predicted by the single-constant theory, and also show smaller colour difference values for some disperse dyes. The results show that the scattering of some disperse dyes cannot be negligible, and that the recipes that match to textiles coloured by these disperse dyes should be predicted using the new two-constant theory.     

Physico-thermal Stabilities of Dye Solids I—Heat Capacities of some Disperse and Vat Dyes

The application of differential scanning calorimetry to a number of pure disperse and vat dye solids to determine their molar heat capacities and to study the changes in this property with temperature is described. The method is used to detect possible solid-state transitions occurring in the dyes on heating. Premonitory positive deviations from linearity are observed with three disperse dyes at temperatures up to 30 deg C below transition or melting points. The results are discussed in terms of Frenkel and Schottky disorder, and the activation energy of this disorder is calculated. For the three vat dyes examined, the heat capacity passes through a maximum on heating. The subsequent decrease in heat capacity is possibly due to an increase in lattice order caused by localised sublimation in void spaces within the crystals.     

Determination of colour sensitivity of dye mixtures for disperse dyes

A method has been developed to quantify the colour sensitivity of a dye mixture. In this method, the concept of the colour sensitivity of matching recipes has been developed so that it covers variations, not only in dye concentrations, but also in dyeing parameters. Firstly, the 'individual colour sensitivity' of a dye mixture to a specific dyeing parameter was quantified by comparing the colour difference between the resulting shade from a normal dyeing condition and that produced by giving a change to the parameter. These resultant data were used to calculate the total colour sensitivity covering the factors, temperature, time and liquor ratio, with a model established based on CMC(2:1) equation. This calculated result simulates the reproducibility of a dye mixture in the dyeing application under certain accuracy of the dyeing process control. A set of dye recipes was applied by dyeing to verify the calculation with disperse dyes on polyester.     

Dyeing of N-modified viscose rayon fibres with acid and metal-complex dyes

Viscose rayon N -modified by the incorporation of polydiallyldimethyl ammonium chloride gave good dye exhaustion and colour yield on dyeing with acid or metal complex dyes. The amount of additive present in the fibre was assessed from its nitrogen content, and percentage exhaustion was found to increase with increasing quantity of additive. Changes in hue, in addition to an increase in the light fastness of deeper shades, are attributed to aggregation of dye within the fibre. The light fastness of metal complex dyes on N -modified fibre was very good but acid dyes gave poor results. Wash fastness was improved after treating with a dye fixing agent.     

The thin layer chromatography of vat dyes

The identification and separation of vat dyes by thin layer chromatography has been investigated with reducing and non-reducing systems. The results showed that the chromatograms on silica gel plates obtained by non-reducing systems at 100 or 120°C were fast, reproducible and easy to control. Nine non-reducing eluents were developed, producing good migration and resolution of 21 vat dyes. Analyses of the chromatograms revealed that the R_f, values varied with the temperature of the system, the chemical structure of the vat dyes and the nature of adsorbent, as well as with the eluents used. The effects of molecular masses of the vat dyes on the R_f values were less significant. Despite the successful use of a novel reducing agent for vat dyes, the chromatography of reduced dye was largely unsatisfactory. The use of reversed-phase t.l.c. plates was examined and showed little benefit.     

高速胶体磨和高压均质机在染料加工中的应用

高速胶体磨和高压均质机用于分散染料和还原染料可使染料粒径小于2μm，甚至低于1μm，选用合适的分散剂，配合其它相关助剂，可有效提高商品染料的质量本文推荐了若干实用的染料加工配方。     

Colour in textile effluents – sources,measurement, discharge consents and simulation: a review

This paper aims to review the problem of colour in textile effluents, the different classes of dyes available and their contribution to the problem. Through new regulations, pressure is being placed on water companies all over the world to reduce the amount of colour in sewage effluent. Dyes exhibit low toxicity to mammals and aquatic organisms and therefore colour consents are normally applied for aesthetic and industrial reasons rather than for prevention of toxicity. The absorbance, ADMI values and concentrations of dyes in effluent are examined here with particular reference to reactive azo dyes used in cotton processing. Colour consents, the problem of colour in textile wastewaters and the importance for research in this area are also discussed. Dye concentrations of 0.01 g dm⁻³ up to 0.25 g dm⁻³ have been cited as being present in dyehouse effluent, depending on the dyes and processes used. ADMI values ranged from 50 to 3890 units for the dyeing of cotton. It was concluded that 1500 ADMI units was a reasonable value to aim for when simulating coloured effluents. Simulated textile effluents may be used for research purposes. These should resemble real wastes as closely as possible, but it is often difficult to replicate the ADMI values, absorbance and spectra of real effluents. The concentrations of dye used in simulated effluents examined in literature varied from 0.01 g dm⁻³ to 7 g dm⁻³. As absorbance and ADMI values change with the types of dye used, it is difficult to relate these values to dye concentrations. A concentration of 0.18 g dm⁻³ of a Red or Yellow dye or 0.43 g dm⁻³ of a blue dye would provide an ADMI of approximately 1500 units and fits within the range of dye concentrations presented in literature. A dye mixture simulating colour in a real textile effluent is suggested and some limitations of simulating actual wastewaters discussed. © 1999 Society of Chemical Industry     

The reduction of vat dyes by indirect electrolysis

The reduction of vat dyes by an indirect electrolytic process is described. The dyeing procedure and the relevant dyeing parameters for this new reduction technique are discussed. The dyeing results are comparable with those obtained by standard experiments using sodium dithionite. After removal by filtration techniques of the remaining dye from the exhausted dyebath, regeneration of the reducing agent by cathodic reduction is possible. The results demonstrate the applicability of this reduction method for larger-scale vat dyeing procedures.     

A New System of Continuous Flash Dyeing

This paper describes work carried out during the development of a new ‘Flash’ continuous-dyeing system for cellulose-based fabrics. The new system was aimed primarily at the successful application of vat dyes, which worldwide still account for very substantial yardages and form a high proportion of fabric which is continuously dyed. Earlier investigations had shown that novel methods held promise, but perhaps not sufficient to displace current techniques. The conventional pigment pad-hot flue-chemical pad-steam sequence has long been preferred for high quality vat dyeing, but changes in recent years have made it clear that alternative systems could find favour. These changes include:

• 1 Much shorter runs per colour.
• 1 Blends with other fibres, especially with polyester.
• 1 Higher operating costs (labour, water, energy, dyes, etc.) which call for a reduction in downtime due to colour changes, and the need for more accurate recipe formulations without recourse to instrumental prediction techniques.

These changes in trading conditions, along with the high capital cost of the preferred conventional equipment, have made economic processing more difficult. The new process is a simple pad system with an ‘all-in’ dye bath. Deep dyeings of normal fastness can be readily obtained. Recipe formulations for production can be predetermined in the laboratory. The time for a complete change of colour varies from I minute for pale-medium dyeings to 5 minutes for deep dyeings. Dye yield is excellent. Space requirements are halved and energy (motive power and steam) demand is cut by two-thirds.     

In situ hypochlorous acid generation for the treatment of textile wastewater

An electrolytic process based on chlorine generation was adopted to treat wastewater containing textile dyes. In situ production of hypochlorous acid was achieved in an undivided electrolytic cell. The cell contained a graphite rod as the anode and a stainless steel sheet as the cathode. The generated chlorine reacts with water leading to the formation of hypochlorous acid and hydrochloric acid. The resultant hypochlorous acid, being an oxidising agent, oxidises the organic components present in the textile wastewater. In this study, the colour in wastewater containing Procion Navy and Procion Red dyes, respectively, was completely removed after 40 min of electrolysis at a constant current density of 39 mA/cm² (where the initial dye concentrations were 3700 and 3200 mg/l, respectively). In the case of the Procion Yellow and composite dyes, complete colour removal occurred after 50 min of electrolysis (with initial dye concentrations of 3500 mg/l). Even though colour removal occurred during the electrolysis process, it required up to 180 min of electrolysis to reduce the COD values for the four dyes (Procion Navy, Red, Yellow and the composite) from the initial levels of 4520, 4200, 4170 and 4283 mg/l to 70, 45, 39 and 52 mg/l, respectively. This clearly indicates that the process removes both colour and organic components present in textile wastewater.