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.     

Optimisation of the colour sequence in the process of fabric dyeing

When programming a dyeing machine, a sequence of colours has been established in an attempt to reduce the effects caused by dye residues on the colours that are subsequently applied. In this paper a model is presented that makes it possible to determine the optimum sequence. Using a optimisation method, the sequence that minimises the sum of the photocolorimetric differences between the colours required and those obtained has been determined. In order to estimate the change that each colour undergoes due to the presence of residual dye in the dyeing equipment a computer calculation method has been adopted.     

Fuzzy control of dyebath pH in exhaust dyeing

In textile exhaust dyeing, the control of dyebath pH is a critical factor in order to achieve optimum colour yield and levelness. Conventional controllers have not proved entirely successful in controlling dyebath pH since it is difficult to develop an exact mathematical model for the dyeing process. One method is to apply fuzzy control to the dyeing process. For the fuzzy controller to operate successfully, it is important to understand how the dyeing system responds to given reference pH/time profiles. A dynamic model for the dyeing process has been developed and this allows the fuzzy controller to be fine-tuned by computer simulation. Results of the control system simulation showed very satisfactory tracking performances of the pH profiles. This provides a starting point for further fine-tuning of the system under practical dyeing conditions.     

Optimisation of the colour sequence in the dyeing process: industrial applications

In this paper we report, for realistic industrial work conditions, the applicability of the optimisation model developed to obtain the best colour sequence in the process of fabric dyeing. We have resolved the problem of ordering a long series of colours using a personal computer, to establish an optimum order. This takes into account the perceptual response of the human eye. The sequence begins with one specific colour, returning, under certain conditions, from dark to light colours. The algorithm we developed considerably reduces the number of determinations that must be carried out within a colorimeter.     

分散染料染合成纤维上染过程集成建模

在纺织染色中,分散染料染合成纤维是比较重要的典型染色组合之一。通过对已有染色理论和人工经验的结合,以分散蓝RSE染涤纶为代表,建立分散染料染合成纤维的上染过程数学模型。在建模时,首先建立3个与温度有关的独立的上染特性模型,然后运用反应速率方程将已建立的3个模型集成起来,最终建立染料上染量-时间集成模型。在模型建立过程中,由于使用了具有少数据性和较高精确性特点的灰色Verhulst理论,从而使得集成模型中的参数值容易确定,计算量小。对于同类型的染料,改变参数值模型即可同样适用。上染过程建模实验表明,此数学模型有较高的精确度和很好的泛化能力,可以满足对染色结果进行预测的需要。     

Optimisation of the colour sequence in the dyeing process: washing the equipment

Two models have been developed in this paper. The first considers the way the colour obtained is affected by dyestuff residuals, while the second takes into account the financial cost of washing the dyeing equipment. Both are equivalent and complement each other when washing is essential. The models can be adapted to suit different business policies and can be solved using a standard algorithm for the asymmetric travelling salesman problem.     

浅谈分散染料染色残液COD

该文通过打小样试验,挑选适用于碱性染色工艺和弱酸性染色工艺的两种不同染料各九支,并结合实际生产中大部分染厂所用工艺,应用三种不同工艺对涤纶织物进行上染,收集染色残液测量pH和COD．使用碱性染色工艺,染液在织物上染前后pH值有变化,残液pH值达到GB4287—92中的相关规定;使用弱酸性染色工艺和染厂所用工艺,染液在织物上染前后pH基本没有变化．对比三种工艺收集残液的COD值,发现使用碱性染色工艺的分散染料,收集的残液COD明显偏低。这为大生产中印染厂优化染色工艺、节能减排、降低综合成本提供了试验依据。     

Dyeing process in a finite dyebath

The processes of adsorptive and reactive dyeings of polymer film in a finite bath were formulated on the basis of pore model concept. The influence of the bath ratio on the fractional uptake or fixation was numerically analyzed. The time of half-dyeing is proportional to the bath ratio to the power of about 0.9 within the present computational conditions. This fact is in contrast to the finding that, in an infinite bath with the same dye concentration as the initial value in a finite bath, the time of half-dyeing is inversely proportional to the dye concentration. The relation of the total uptake or fixation to the dimensionless dyeing time θ multiplied by γ^0.9 is independent of the bath ratio within an error of 5% or 8%.     

pH control for dyeing polyamide in a reused acid dyebath

The pH control that can be achieved in a reused dyebath was investigated. The study involved a phosphate buffer system and four pH sliding systems, including ammonium sulphate and three hydrolysable organic esters. Instead of discharging the dyebath after each dyeing cycle, the residual dyebath was analysed using a UV-Vis spectrophotometer and reconstituted to the required concentration of dyes, auxiliaries and acid donors. The dyebath was reused for 10 cycles and colour reproducibility, levelness and fastness of the dyed samples were measured after each recycling. In comparison with ammonium sulphate and sodium dihydrogen phosphate, hydrolysable organic esters gave a stable and effective pH shifting in the dyebath reuse system. In addition, hydrolysable organic esters resulted in a very low amount of salt in residual dyebath. No deterioration in colour fastness of the dyed fabrics over 10 cycles of dyebath reuse was evident.     

Waterless dyeing of polylactic acid with disperse dyes using decamethylcyclopentasiloxane as medium

Polylactic acid (PLA) fibre as a new generation of eco-friendly polyester fibre is expected to substitute polyethylene terephthalate (PET) fibre to be an important textile fibre raw material. However, there exist severe strength loss and light dyeing colour by the traditional water bath dyeing method, which seriously affect the promotion and application of PLA fibre in the textile fields. Therefore, it is necessary to study waterless dyeing method for PLA. Decamethylcyclopentasiloxane (D5) possesses excellent physical and chemical properties with the characteristics of odourless, non-flammable, and stable to various chemicals, which has been studied to be used as a waterless dyeing medium for PET fabric. In this study, D5 was selected as the medium to study the waterless dyeing process and properties for PLA. The effects of disperse dye dosage, dyeing temperature, dyeing time and liquor ratio on the dyeing properties of PLA fabric were investigated. The results showed that the optimal dyeing process conditions were as follows: the dye dosage was 4%, dyeing temperature and time were 120°C and 40 min, respectively, and the liquor ratio was 1:10. Then PLA was dyed by three different colour disperse dyes using the optimal process which were compared with the traditional water bath. The results showed that the properties of dyed PLA fabrics with D5 could reach the dyeing effect of the traditional water bath method, while causing less influence on its mechanical property. Therefore, this research proved that D5 can be used as a dyeing medium for PLA fabric to substitute the traditional water bath dyeing.     

HAO分散蓝的制备及其染色性能

采用3-氨基-5-硝基苯并异噻唑为重氮组分,设计与合成了一支耐碱分散染料,探究了染料的光谱性能、耐碱性、耐氧化性、提升力性能及染色织物的各项牢度。核磁氢谱验证了合成染料的化学结构。紫外可见分光光度仪分析表明染料为蓝绿色,具有20 000 L/(mol·cm)以上的摩尔消光系数。应用结果表明,染料具有优良的耐碱性能和高的耐氧化性,能够满足涤棉织物碱减量氧漂一浴法染色的工艺要求,同时该染料还具有较高的染色提升力,染色的涤纶织物具有较好的水洗、日晒、升华和摩擦牢度。     

Fundamental studies on solvent dyeing with tetrachloroethylene. III. Effect of water added to the solvent dyebath on the diffusion of disperse dyes in poly(ethylene terephthalate)

The diffusion and adsorption of disperse dyes on poly(ethylene terephthalate) (PET) from the tetrachloroethylene (TCE) dyebath were investigated by the method of cylindrical film roll when water was added to the TCE dyebath. The diffusion coefficients of three disperse dyes were increased with an increase in the addition of water to the TCE dyebath, and that of C.I. Disperse Violet 8 showed a peak. The solubilities of water in TCE in the absence and presence of disperse dye were measured at 90°C by Karl Fischer titration. The solubilities in TCE were 0.040 in the absence of dye and 0.041–0.045 g H₂O/100 g TCE in the presence of disperse dye. In the presence of Violet 8, the solubilities showed a peak with increasing addition of water. The effect of water addition on the diffusion coefficients was attributed to the dissolution of water in the TCE dyebath. The water dissolved in TCE brought about an additional swelling of PET swollen previously by TCE. No marked influence on the surface concentration of dye was observed by the water addition to TCE.     

Vapor phase dyeing of synthetic fibers with disperse dyes

Dyeing of synthetic fibers by the heat transfer process of disperse dye vapors is performed by contacting white receptor polyester or polyamide fabric with other dyed polyester fabrics (donor) under the influence of heat. The dye vapours flowing away will diffuse across the very slight air gap enclosed between the inner donor and receptor surfaces under the applied pressure. It is found that the dye uptake by the receptor fabric is dependent on the original dye content of the donor fabric, transfer temperature and dwell time. The released dye from the donor fabric under the influence of heating is found to be dependent on the original dye content of the donor fabric as well as the transfer temperature. The efficiency of the dye transfer is also attributed to the original shading of the donor fabric. Evaluation of the imparted colors on the receptor fabric (polyester, polyamide) obtained by heat contact with the same donor fabric showed visually the same colour level up to the 13th run. Thermodynamic interpretation of the standard affinity (Δu⁰) and heat of dyeing (ΔH⁰) as well as the partition coefficient of the dye show that the dyeing process has an exothermic character. The rate controlling step in this dyeing process is found to be dependent on the diffusion of the dye vapors into the fiber phase.     

Limitations in predicting dyebath exhaustion using optical spectroscopy

There are practical limitations in predicting dyebath concentrations and dyebath exhaustion using absorbance measurements from optical spectroscopy. The purpose of this paper is to examine the common assumptions of prediction models that cause prediction errors, and especially when multiple dye combinations are used. If a linear model is used to map absorbance to concentration, then five assumptions must hold: measurement repeatability, linear scaling, spectral additivity, linear independence of the constituent spectra and the absence of spectral morphing. Violation of one or more of these assumptions will lead to errors in predicting the concentrations of dyes in a dyebath and subsequent exhaustion calculations.     

The dyeing of nylon with a microencapsulated disperse dye

Melamine resin microcapsules containing CI Disperse Blue 56 were prepared by in situ polymerisation. The microcapsules were characterised by their thermal properties and morphology, such as particle size and particle size distribution. The dyeing behaviour of the microcapsules on nylon 6.6 was evaluated. The microencapsulated dye exhibited good build-up, levelness and fastness properties. It has been demonstrated that microencapsulated disperse dye can be used to replace commercial disperse dyes in dyeing polyamide fabric without dyeing additives, and the resulting effluent can be easily recycled after filtration.     

Pad dyeing of cellulose acetate nanofibres with disperse dyes

In addition to a number of applications of nanofibres in technical fields such as medical, filtration and biosensing, nanofibres are recently being widely explored in terms of apparel use. Past work has focused on the functional properties of nanofibres for apparel use. Coloured nanofibres were produced to investigate their aesthetic properties for the potential application to apparel. Webs of cellulose acetate nanofibre were electrospun and dyed with a high energy level CI Disperse Red 167:1 dye and a low energy level CI Disperse Blue 56 dye using the continuous pad–dry–bake method. Results revealed that the high energy level dye produced better colour yield than the lower energy level dye. The dyed cellulose acetate nanofibres produced acceptable colorimetric values, colour yield and colour fastness. Young’s modulus of dyed nanofibres increased by threefold in comparison to the undyed cellulose acetate nanofibres. Scanning electron microscopy images showed good morphology with the smooth surface of the dyed cellulose acetate nanofibres.     

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.     

Carrier dyeing of polyphenylene sulphide fabric with disperse dye

Polyphenylene sulphide is considered to be a high‐performance thermoplastic material and has been used in many areas over the past few decades. But the application of polyphenylene sulphide fabric used for protective clothing is limited because of difficulties in its dyeing and printing. In this work, carrier dyeing of polyphenylene sulphide fabric with disperse dye is discussed, and the effect of the structure of the carrier, dyeing temperature, dyeing time, usage of carrier and usage of dye on colour strength of the dyed sample and the percentage of dye exhaustion were investigated. In addition, the glass transition temperature, crystalline structure and orientation degree of treated polyphenylene sulphide fibre with benzyl benzoate were measured by differential scanning calorimetry, X‐ray diffraction analysis and velocity‐oriented tester, respectively. The results indicated that benzyl benzoate could increase the percentages of dye exhaustion and colour strength values, while at the same time reduce the glass transition temperature and orientation degree of the treated polyphenylene sulphide fibre. Thus, it would be beneficial to the diffusion of the dye molecules into the amorphous region of the fibre. Furthermore, the decrease of tensile strength and limiting oxygen index of the dyed polyphenylene sulphide sample was very little, and the colour fastness and levelness of the dyed polyphenylene sulphide samples were also satisfactory.     

One‐step dyeing of polyethylene terephthalate fabric,combining pretreatment and dyeing using alkali‐stable disperse dyes

In the conventional dyeing process, polyester and its blended fabrics are usually dyed in a weak acidic medium. In order to reduce cost and improve production efficiency, a new dyeing method – one‐step dyeing of polyethylene terephthalate fabrics, combining pretreatment and dyeing in alkali conditions – was investigated. The alkali‐stable disperse dyes Red 900, Red 902, Yellow BROB and Blue 825 were used to dye polyethylene terephthalate fabrics. The dyeing properties of polyethylene terephthalate fabrics in the case of one‐step dyeing at various pH values or sodium hydroxide concentrations were discussed in terms of colour yield, colour parameters and fastness. The performance of one‐step dyeing using alkali‐stable disperse dyes was excellent. The dyed fabric had good fastness. Wet processing could be combined and shortened. One‐step dyeing of polyethylene terephthalate fabrics could reduce the consumption of water and energy and improve production efficiency. One‐step dyeing of polyethylene terephthalate has potential application in cleaner textile production.     

The mathematical expression of rate constants in empirical rate of dyeing equations in disperse dyeing

The relationship between the rate constants in empirical rate of dyeing equations and the diffusion coefficient of dye in the fibre have been clarified by means of a statistical curve fitting method, where the rate of dyeing curves calculated from the theoretical equations (those of Wilson and Newman) have been compared with those from the empirical equations in the range M_t/M∞ from zero to about 0.8. The comparisons revealed that many of the empirical equations are suitable for describing the dyeing rate when there is a delay of dye sorption in the early stages, and one of them is useful for determining the dyeing rate when there is rapid dye sorption at the initial stages. The fact that these empirical equations fit well to practical dyeing can be explained in terms of the sorption delay caused by the stagnant solution layer surrounding the fibres.