The influence of polymer and dye characteristics on diffusion in nylon 66

A study has been carried out of the relationship between polymer orientation and dyeing behavior using a specially prepared range of nylon 66 samples varying only in orientation and five dyes normally showing varying degrees of sensitivity to physical variations in nylon. Integral diffusion coefficients have been calculated using Crank's finite dyebath equation from appropriate rate of dyeing data. Evidence has been produced which suggests that except with dyes of low molecular weight, i.e., dyes insensitive to physical variations in the nylon, a diffusional interaction between diffusing dye molecules exists which leads to a variation in the concentration dependence of the diffusion coefficient with fiber orientation. The length of the diffusing dye ion has been shown to be of decisive importance in this interaction.     

Kinetics of thermo-fixation of solvent dyes and pigments in polyester fibres

The diffusion coefficient of a dye in fibres is critical to understanding the dyeing process and coloration quality of products. In this paper, the diffusion kinetics of solvent dyes in the thermosol dyeing of polyester fibres was studied by measuring K / S of the dyed polyester fabrics based on the Kubelka–Munk equation. The diffusion coefficients of two model solvent dyes were estimated with Hill's equation using the experimentally measured K / S values and were found to be in good agreement with those calculated from the traditional extraction method. Such a measurement method was applied to several other solvent dyes and pigments that have different molecular sizes and a good correlation between the measured diffusion coefficients and sizes of these dyes and pigments was found. The results indicate that it is feasible to use K / S measurement of dyed fabrics and Hill's equation to evaluate the kinetics of the thermosol dyeing process under certain conditions.     

Solvent dyeing of acrylic fibers. Process variables and mechanisms based on rates of dyeing and diffusion studies using cationic dyestuffs

Diffusion coefficients of selected cationic dyes are calculated for one aqueous and six organic solvent dye systems. The concentrations of dyestuffs sorbed by the fibers as functions of dyeing times are plotted for the various dyeing systems. Results indicate that dye sorption decreases and the diffusion coefficient increases as the concentration of the cosolvent increases. The results were determined by comparing the Crank and Olofsson equations for diffusion.     

Chemical Engineering Aspects of Dyeing Processes

Abstract

First, existing research on diffusion of disperse, reactive, and ionic dyes in polymers and correlation of the rate of dyeing to the operating variables in the dyebath is reviewed. Second, to discuss the kinetic aspects of various dyeing processes, the dyeing of textiles is classified into two categories: adsorptive and reactive dyeings, and these two dyeing processes are modeled in terms of diffusion of dyes in polymers accompanied by some physicochemical interaction with the polymer substrates. The process of adsorptive dyeing was formulated on the basis of a dual-mode sorption and mobility model where the porelike region was conveniently invoked. The calculated profiles of the concentration of immobilized dye are similar to the measurments of dye distribution curves by means of film-roll, microdensitometric, and microspectrophotometric techniques. The outline of formulation of the process of dyeing with reative dyes (i.e., reactive dyeing) is given on the basis of diffusion of dye within the fiber accompanied by a fixation reaction incorporating hydrolysis of dye species. It is concluded from numerical analysis that the lower the bath ratio, the less the decrease of the final fixation due to hydrolysis of the dye and the less the influence of mixing in the dyebath on the fixation. When the fixation reaction is slow, the final futation is almost independent of the bath ratio and the degree of mixing.     

Basofil纤维分散染料染色性能研究

选择了4只蒽醌结构和2只偶氮结构的分散染料，用于Basofil纤维的染色，用0.5molHCl和DMF在高温条件下将纤维上的染料萃取完全后、染料的最大吸收峰不变：在染色达到平衡时，测定了纤维上染料的浓度，结果显示：分子结构小、具有共平面的蒽醌染料适合上染Basofil纤维。染料的扩散系数和扩散活化能随染色温度上升而明显增加，其中C.I.Disperse Blue 56在纤维中扩散速度最快实验结果表明：染料的分子结构越小，染料上染量越大，扩散系数和扩散活化能的研究也揭示了相同的规律.     

The Determination of Diffusion Coefficients as a Function of Concentration for Dyes in Fibres

A method of determining the dependence on dye concentration of the diffusion coefficient of dyes in fibrous substrates has been developed, based on an approximation method of Crank, in which the amount of dye adsorbed by the fibre is measured colorimetrically as a function of time. The method has been applied to two dyeing systems, the direct dye Chlorazol Sky Blue FF (C. I. Direct Blue 1) on rayon and the acid dye Naphthalene Scarlet 4R (C. I. Acid Red 18) on nylon 6. 6. The results are in good agreement with those of R. H. Peters et al. for the same dyes and substrates, although Peters used films and not fibres and determined diffusion coefficients by an experimentally more complex method that appears impractical for fibres, the film being sectioned and the dye concentration measured as a function of distance with a microdensitometer.     

The absorption of direct dyes by crosslinked cellulose. II. Rate of dyeing and diffusivity

The effect of crosslinking in the dry state on the rate of dyeing of cellophane with two direct dyes, Chrysophenine G and Chlorazol Sky Blue FF, has been studied. Dimethylolethyleneurea and bis(hydroxyethyl) sulfone were the crosslinking agents. It was found that the rate of dyeing was reduced at high degree of crosslinking by more than 90%, whereas the amount of dye absorbed at equilibrium was reduced by only 40%. It was concluded that the major factor in the practical undyeability of the crosslinked cellulose fibers in commerce is the reduction of the rate of dyeing rather than that of the absorption at final equilibrium. The average diffusivities of the dyes in the cellulose film were calculated from the rate data. The diffusion coefficients as functions of the dye concentration in the films were estimated from the diffusivity values. The two models of swollen cellulose, the pore model and the gel model, were applied to explain the effect of crosslinking on the diffusion coefficients. The pore model offers a satisfactory explanation by assuming that crosslinking reduces the average pore diameter and therefore increases the drag and also the tortuosity. The gel model offers an equally satisfactory explanation by assuming that crosslinking reduces the free volume by increasing the rigidity and concentration of the cellulose chains in the cellulose gel.     

Diffusion of disperse dyes into super-microfibres

The disperse dyeing process for polyester fibres is complex. It is characterised by the diffusion-controlled sorption of dyes and depends on dye concentration, dyebath temperature, dye liquor flow rate and fibre count. Moreover, the dyeing properties of super-microfibres are also quite different from those of microfibres or conventional polyester fibres. In this paper the influence of dyebath temperature, initial dye concentration and fibre count on the diffusion coefficient and the sorption isotherms has been studied. The analysis of kinetic properties has been restricted to infinite dyebath conditions. All experimental results have been compared terms of fibre count and dyebath temperature.     

Dyeing kinetics of methacrylic acid grafted polyester fabric with astrazonrot violet and rhodamine red basic dyes

The low‐temperature dyeing kinetics of radiation‐grafted poly(ethylene terephthalate) fabric were studied. The effects of the graft yield (GY), dye concentration, and dyeing temperature on the color difference (CD) of methacrylic acid grafted polyester fabric were studied for astrazonrot violet (AV) and rhodamine red (RR) basic dyes. CD increased sharply with an increase in GY and tended to level off at higher degrees of grafting. The best dyeing conditions were achieved for both dyes at pH 11.5. CD of the grafted fabric increased rapidly as the dyeing time increased; this was followed by a relatively slow dyeing rate within a few minutes, which depended on the concentration and temperature of the dye bath. The initial dyeing rates and rate constants for the AV dye were higher than those for the RR dye. The dyeing process followed 0.14‐order kinetics and was independent of the dyeing temperature or the type of dye. The dyeing rates and rate constants increased with an increase in the dyeing temperature. An Arrhenius‐type plot of the natural logarithm of the dyeing rate constant versus the inverse of the absolute temperature yielded apparent activation energies of 4.9 and 13.8 kJ/mol and pre‐exponential rate constants of 9.4 and 100.6 (CD/GY)s^?1 for the AV and RR dyes, respectively. The mechanism of the dyeing process for the two dyes was diffusion‐controlled, and their dyeing rates depended on the type of basic dye. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1070–1076, 2004     

Diffusion mechanism of direct dyes into a cellulose membrane: The structural effect of direct dyes on the adsorption rate

The transport of three typical direct dyes, C.I. Direct Yellow 12, C.I. Direct Red 2, and C. I. Direct Blue 15, into a cellulose membrane has been studied at 55°C. Sodium chloride was used as a stimulator for dyeing. The effects of the concentration of the stimulator on the adsorption isotherms, the adsorption rate, and the concentration profiles in the membrane were tested. The experimental adsorption rates of three dyes were quite different. The diffusion mechanism of the dyes into a cellulose membrane was analyzed on the basis of the parallel transport equation of surface and pore diffusion as developed in our previous paper. The experimental uptake curves showed good agreement with the theoretical curves for surface diffusion control. Experimental concentration profiles also agreed reasonably well with the theoretical lines for surface diffusion control rather than pore diffusion control. The surface diffusivities of three dyes were quite different and nearly independent of the adsorbed phase concentration of the dye.     

Disperse dyeing of polyester fibers: Kinetic and equilibrium study

The effect of temperature on the dyeing rate constant k, diffusion coefficient D, and time of half‐dyeing t_1/2 was evaluated for the dyeing of polyester fibers with two disperse dyes, an azo and an anthraquinone dye. Activation energies of diffusion E were calculated. The polyester dyeing equilibrium was also studied and the partition coefficient K and standard affinity Δμ° at various temperatures were determined for the anthraquinone dye. Standard enthalpy ΔH° and standard entropy ΔS° of dyeing were also obtained. The same equilibrium parameters were not obtained for the azo dye because of its dyeing behavior. A similar kinetic and equilibrium study was made for the pure azo and anthraquinone compounds free from the dispersing agents present in the commercial dyes and the results are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 123–128, 2002     

The Dyeing of Polyester Textile Fabric in Perchloroethylene by the Exhaust Process

The dyeing behaviour of disperse dyes in perchloroethylene is considered. In particular, the relationship between distribution equilibrium and colour yield, the effect of auxiliary solvents on colour yield, the effect of water on the dyeing mechanism, the dependence of the colour yield on the amount of water and time and temperature of dyeing, and the effect of auxiliary solvents on the colour yield in water-containing perchloroethylene liquors are discussed. The stripping of dyes from polyester with trichloroethylene is mentioned. Finally, the selection of dyes for use in the dyeing of polyester from perchloroethylene by exhaust processes is considered. The desire for a solvent-based dyeing process can be fulfilled. Dyeing of polyester from perchloroethylene can offer a number of technical advantages which make it a genuine alternative process to the conventional dyeing methods.     

Disperse dyeing of polyester fibers: Kinetic and equilibrium study

The effect of temperature on the dyeing rate constant k, diffusion coefficient D, time of half‐dyeing t_1/2 was evaluated for the dyeing of polyester fibers with two disperse dyes, an azo and an anthraquinone dye. Activation energies of diffusion E were calculated. The polyester dyeing equilibrium was also studied and the partition coefficient K and standard affinity Δμ° at various temperatures were determined for the anthraquinone dye. Standard enthalpy ΔH° and standard entropy ΔS° of dyeing were also obtained. The same equilibrium parameters were not obtained for the azo dye because of its dyeing behavior. A similar kinetic and equilibrium study was made for the pure azo and anthraquinone compounds free from the dispersing agents present in the commercial dyes and the results are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2785–2790, 2002; DOI 10.1002/app.10254     

Concentration Dependence of the Diffusion Coefficients of Disperse Dyes in Polyethylene Terephthalate

Diffusion coefficients of disperse dyes have been calculated by Matano's method from diffusion profiles in polyethylene terephthalate(PET). The diffusion coefficients (D_c) clearly indicate concentration-dependence. It has been found, from the densities of the dyed PET and the dye, that there is no overall change in the volume of the PET and dye in dyeing. The instrinsic diffusion coefficients have been calculated from D_c and the volume fraction (φ₁) of penetrant in the amorphous region. From these values, thermodynamic diffusion coefficients (χ?) were obtained. It has been found that the relation between 1/log (χ?/χo) and 1/φ₁ is a straight line, and it therefore seems reasonable to assume that the diffusion of disperse dyes in PET can be described by Fujita's ‘free volume theory’ for the diffusion of low molecular-weight organic compounds in an amorphous high-polymer.     

Effect of microencapsulation on dyeing behaviors of disperse dyes without auxiliary solubilization

Microencapsulated disperse dye can be used to dye hydrophobic fabric in the absence of auxiliaries and without reduction clearing. However, little available information for dyeing practice is provided with respect to the effect of microencapsulation on the dyeing behaviors of disperse dyes. In this research, disperse dyes were microencapsulated under different conditions. The dyeing behaviors and dyeing kinetic parameters of microencapsulated disperse dye on PET fiber, e.g., dyeing curves, build up properties, equilibrium adsorption capacity C_∞, dyeing rate constant K, half dyeing time t_1/2, and diffusion coefficient D were investigated without auxiliary solubilization and compared with those of commercial disperse dyes with auxiliary solubilization. The results show that the dyeing behaviors of disperse dye are influenced greatly by microencapsulation. The diffusion of disperse dyes from microcapsule onto fibers can be adjusted by the reactivity of shell materials and mass ratios of core to shell. The disparity of diffusibility between two disperse dyes can be reduced by microencapsulation. In addition, the microencapsulation improves the utilization of disperse dyes due to no auxiliary solubilization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

An Experimental Study of the Dyeability of Barry Nylon Fibre with Acid Dyes

When nylon fibre is dyed with acid dyes, the rate of diffusion into the fibre depends on the draw to normal ratio than for one more highly drawn. The ratio of the diffusion coefficients for two such substrates is independent of both the dye used and the amount of dye fixed on the fibre. The differences which appear in the dyeing of barry nylon textiles relate to the time parameter Dt/r² (D is the diffusion coefficient in cm² /s, t, the dyeing time in s, and r, the substrate radius in cm). The greater this parameter, the better is the coverage of barriness arising from variations in the draw ratio. Since the diffusion coefficient for a given substrate is specific to the dye, acid dyes differ in their suitability for dyeing barry nylon textile fabrics.     

The mechanism of carrier dyeing

The accelerated rate of diffusion of disperse dyes into synthetic fibers caused by various dyebath additives (“carriers”) has been correlated with their plasticizing action. The rate of change in length of Acrilan filaments with temperature under dyebath conditions enabled the effects of the carrier on the T_g of the filaments to be measured, and the results for different concentrations of carrier at one temperature could be superimposed on a common curve by employing suitable shift factors. The shift factors, as well as the variations of the diffusion coefficients of dyes with temperature and carrier concentration, both matched a WLF relationship, confirming that the dyeing process is controlled by the segmental mobility of the polymer. Indirect experimental evidence suggests that the same relation will describe the effect of carriers on the dyeing of poly(ethylene terephthalate) substrates with disperse dyes.     

涤/棉混纺织物分散/活性染料一浴染色工艺研究

本实验选择双一氯均三嗪结构的活性染料和耐碱型分散染料,探讨涤/棉(65/35)混纺织物分散/活性染料一浴染色工艺。通过单因素实验分析了染色温度、染色时间、无水硫酸钠浓度和碳酸钠浓度对织物染色效果的影响,得到优化的工艺。红色在硫酸钠60 g/L、碳酸钠2 g/L、温度120℃、时间30分钟工艺条件下染色;蓝色在硫酸钠浓度45 g/L、碳酸钠浓度2g/L、温度130℃、时间60分钟工艺条件下染色。     

Reactive dyeing systems for wool fibres based on hetero-bifunctional reactive dyes. Part 2: Investigation of dyeing properties during the dyeing cycle

The dyeing behaviour during the dyeing cycle of a Sumifix Supra dye and some other commercial reactive dyes under various dyebath pH conditions was investigated. Studies of the dyeing of wool serge fabric indicated that the diffusion properties of hetero-bifunctional Sumifix Supra dyes generally lie between those of b-sulphatoethylsulphone (Remazol dyes) and monochlorotriazine (Procion H dyes).