Dyeing natural fibres in supercritical carbon dioxide using a nonionic surfactant reverse micellar system

A reverse micellar system in supercritical carbon dioxide has been developed as a dyeing medium. Water-soluble dyes such as reactive dyes and acid dyes could be sufficiently solubilised in the interior of a specially constituted reverse micelle. Protein fabrics, silk and wool, were satisfactorily dyed even in deep shades with conventional acid dyes without any special pretreatment. Cotton cellulose fabric was also dyed with conventional reactive dyes when the electrostatic force of repulsion between dye and cotton was eliminated. Compared to previously proposed supercritical dyeing methods, dyeing of fabrics with this system could be performed at low temperatures and pressures in a short time.     

Dyeing of nylon 66 with a disperse-reactive dye using supercritical carbon dioxide as the transport medium

Nylon 66 fabric was dyed with a disperse-reactive yellow dyestuff which was synthesised in our laboratory, using a supercritical carbon dioxide dyeing process. The structure of the disperse-reactive yellow dyestuff and its covalent bond with nylon 66 fibres were confirmed by FTIR, NMR, EA and MS analysis. The nylon fabric was also dyed with CI Disperse Yellow 3 and the dyeing results compared. Colour yield values were measured for both dyed fabrics, with those of the disperse-reactive dye showing much better values than CI Disperse Yellow 3. Wash fastness of the fabric dyed with the disperse-reactive yellow dye was tested by the ISO 2 method and showed excellent results. Light fastness was tested by the ISO 105 B05 method and the results were satisfactory. The results obtained indicate fabric immersed in supercritical carbon dioxide does not undergo any fibre damage.     

Kinetics of dyeing of polyester with CI Disperse Blue 79 in supercritical carbon dioxide

Polyester fabric was dyed with CI Disperse Blue 79 in supercritical carbon dioxide and the effect of temperature and dyeing time on dye uptake was studied. On raising the temperature at constant pressure the dye uptake gradually increased, reaching equilibrium after 60 min. The diffusion coefficient at different temperatures and the activation energy of the dye on polyester fabric in supercritical carbon dioxide have been determined. The latter was found to be considerably lower than the corresponding figure for conventional dyeing.     

Dyeing poly(lactic acid) fibres in supercritical carbon dioxide

A study has been conducted into the dyeing of poly(lactic acid) fibres in supercritical carbon dioxide. The fibres were completely dyed using disperse dyes at 50 °C as shown by fibre cross-sections, although high colour depths in dark shades still prove challenging. Dye uptake increased significantly at temperatures ≥80 °C. At 95 °C in supercritical carbon dioxide, shrinkage and hardening of raw poly(lactic acid) were observed which could partly be overcome by the supercritical carbon dioxide extraction step. Afterclearing with cold supercritical carbon dioxide (to remove unfixed dye after dyeing) decreased the colour depth and led to non-uniform dyeing results on poly(lactic acid). Wash and rub fastness was good to very good also when poly(lactic acid) was not aftercleared in supercritical carbon dioxide. Fibre damage and elongation at break in supercritical carbon dioxide were similar to water.     

Adsorption and fixation behaviour of CI Reactive Red 195 on cotton woven fabric in a nonionic surfactant Triton X‐100 reverse micelle

To achieve the goals of saving water and being salt‐free in the coloration of cotton fabric with reactive dye, nonionic reverse micelles were prepared and optimised with a surfactant, Triton X‐100, n‐octanol and isooctane by injecting a small amount of CI Reactive Red 195 aqueous solution. The adsorption, diffusion and fixation of this dye on cotton fabric in Triton X‐100 reverse micelle and bulk water were then investigated. The equilibrium and kinetic data of the dye adsorption process were evaluated. The colour strength and fixation rate of cotton fabrics dyed in the micelle and in bulk water were also examined and compared. The results indicated that the amount of dye adsorbed increased with the increasing temperature and the initial dye concentration. The dye adsorption process could be described using the Langmuir isotherm and pseudo‐second‐order kinetic equations. It was found that CI Reactive Red 195 showed a stronger adsorption property on cotton fabric in Triton X‐100 reverse micelle than in bulk water without the addition of sodium chloride. Using Triton X‐100 reverse micelle as the dyeing medium offered the reactive dye better diffusion performance within the cotton fibre as compared with bulk water. Moreover, higher fixation of the dyes absorbed on the cotton fibre was achieved when the optimum concentration of sodium carbonate was used as the alkali agent in Triton X‐100 reverse micelle.     

Effect of the addition of a modifier in the supercritical dyeing of polyester

The aim of the work was to investigate the effect of an ethanol addition in the dyeing of a commercial polyethylene terephthalate yarn with supercritical carbon dioxide. The equilibrium uptake in the yarn and the partition coefficients of three azo dyes between the polymer and the fluid phases were experimentally measured under different working conditions and compared with the data obtained without any modifier. It was found that the presence of the modifier increases the dye concentration in the yarn and the solubility of the dye in the supercritical phase, allowing good dyeing results to be obtained under less severe working conditions. The partition coefficient data were also satisfactorily regressed with a semi‐empirical correlation, available in the literature for a different system and here adapted to the partition of a dye between a fibre and a supercritical bath.     

Rope dyeing of fabric in supercritical carbon dioxide for commerical purposes

A novel method for fabric rope dyeing in supercritical carbon dioxide fluid has been successfully developed for the first time for commercial purposes by employing a custom‐built machine. The influence of parameters such as system pressure, temperature, and dyeing time on fabric colour strength was investigated, and the parameters optimised. Moreover, the level dyeing property, reproducibility, and colour fastness were investigated and evaluated under various conditions. The carbon dioxide recycling efficiency and the running costs of the proposed process in comparison with conventional processes for commercial production purposes were also investigated. The rope dyeing results show significant influence of the process parameters on fabric colour strength. Satisfactory and commercially acceptable products with a good level dyeing property, high reproducibility of coloration, and good fastness, rated at 4–5 or 5 for washing and rubbing, were obtained with supercritical carbon dioxide fluid. Moreover, a carbon dioxide recycling efficiency ranging from 92 to 95.2% was possible. In comparison with conventional dyeing processes, running costs were lowered by employing the proposed process and rope dyeing machine.     

Dyeing behaviour of poly(ethylene terephthalate) fibres in supercritical carbon dioxide

A new type of poly(ethylene terephthalate) fibre was developed via a high-speed spinning technique. The dyeing behaviour of this fibre in supercritical carbon dioxide was compared with that of a fibre produced by conventional methods. At lower temperature and pressure, the high-speed spun fibre, which had inherently larger crystallite sizes and lower birefringence, showed a larger dye uptake. However, when the supercritical conditions were elevated to 125 °C and 230 bar, the dye uptake of both types of fibre increased markedly and the difference in dye uptake between the fibres was reduced. The new type of fibre showed slightly higher grades in sublimation fastness tests.     

The Effect of Pressure and Temperature on Supercritical CO2 Dyeing of PET-Dyeing with Mixtures of Dyes

Abstract

Dyeing is supercritical CO2 is one of the most advanced dyeing technologies. The dyeing medium is not water but carbon dioxide in the supercritical state (temperatures above 31°C and pressures above 74 bar).

The effect of pressure and temperature on dyeing of PET in supercritical CO₂ with only one dye and with mixtures of two or three dyes has been investigated.

The variations of pressure (250 in 300 bar) and temperature (70 in 130°C) cause differences in colour, especially when mixtures of dyes are used. The dyed samples were evaluated using colorimetry and the extraction of dyes from the fabric.

The amount of all dyes on the fabric rises with the rising temperature due to the accelerated motion of molecular chains and the formation of the free volume in the fibre, so important for the diffusion of dyes. The change of pressure does not after the amount of fixed dyes significantly, but the ratio between the dyes is changed when dyeing with mixtures of dyes.     

Compatibility of a disperse dye mixture in supercritical carbon dioxide dyeing

The compatibility of three disperse dyes, CI Disperse Orange 30, CI Disperse Red 167 and CI Disperse Blue 79, which are commonly used as a trichromatic combination for conventional dyeing, was studied in supercritical carbon dioxide dyeing. Both the dyeing rate and the build‐up of the selected dyes were measured. Experimental results showed that they were quite compatible. The dyeings of a binary combination (CI Disperse Orange 30 and CI Disperse Blue 79, mass ratio 1:1) and a ternary combination (CI Disperse Orange 30, CI Disperse Red 167 and CI Disperse Blue 79, mass ratio 1:1:1) at different dye concentrations showed an on‐tone uptake and presented the same metric hue angles. This proved that the selected dyes could form a useful trichromatic combination in supercritical carbon dioxide dyeing. Furthermore, the uptake and exhaustion of the single dyes in supercritical carbon dioxide dyeing were similar to those in aqueous dyeing, implying that the dyeing media play only a minor role in the dyeing of polyester fibres with disperse dyes.     

Analysis on the dyeing of polypropylene fibers in supercritical carbon dioxide

Polypropylene fibers were dyed in supercritical carbon dioxide system and the results were compared with those of fiber dyed in water system. Dye uptake value calculated by a UV spectrum indicated that polypropylene fiber dyeing was much better in carbon dioxide than in water. Optical microscopical analysis showed that dye molecules had diffused thoroughly into fiber in CO₂ because of the excellent compatibility between the dye and the CO₂. X-ray and birefrigence analysis demonstrated that plastification caused by the implementation of CO₂ made molecular chain more mobile and led to an increase in the dyeing of polypropylene fibers. Moreover a mechanical test and DSC analysis indicated that the fiber structure was not damaged when the fabric was dyed at 100 °C. Hence dyeing polypropylene using CO₂ as a transport medium was very feasible and worthy of further development.     

未改性聚丙烯纤维的超临界染色研究进展

综述了未改性聚丙烯纤维的超临界染色研究进展。在超临界二氧化碳中,染料可以扩散至纤维内部,与传统的方法相比,染色结果有很大的提高。超临界二氧化碳作为未改性聚丙烯纤维染色媒介是可行的。有25篇参考文献。     

Dyeing of natural fibres from perfluoro-polyether reverse micelles in supercritical carbon dioxide

The dyeing of natural fibres from a reverse-micellar system in supercritical carbon dioxide has been investigated using ammonium carboxylate perfluoropolyether as surfactant. Protein fibres such as silk and wool were satisfactorily dyed in deep shades with conventional acid dyes without special pretreatment. Exhaustion was excellent. It was however found that on these fibres the performance of acid dyes was strongly influenced by temperature and carbon dioxide density. Conventional reactive dyes in this system were adsorbed on cotton, even in the absence of dyeing auxiliaries, but the fixation of the dye was not satisfactory. Compared with supercritical dyeing methods reported previously, it was found in this study that the temperature and pressure required were significantly lower.     

Dye solubility in supercritical carbon dioxide. Effect of hydrogen bonding with cosolvents

The use of supercritical carbon dioxide is emerging as a potential method for achieving pollution-free dyeing. An important factor in supercritical fluid dyeing is the solubility of the dye in supercritical carbon dioxide. Our measurements show that the solubility of C. I. Disperse Red-60 dye in supercritical carbon dioxide is significantly enhanced upon addition of polar csolvents : ethanol and acetone. The solubility enhancement is attributed to the formation of hydrogen bonds between cosolvent and dye molecules. Observed solubility behavior is correlated using dilute-solution theory with lattice-fluid-hydrogen-bonding model. Needed physical and hydrogen-bonding molecular parameters are estimated using the experimental data.     

Adsorption and fixation of a reactive dye on cotton in non-aqueous systems

The dyeability of a reactive dye, CI Reactive Red 2, on cotton in non-aqueous media has been investigated using a reverse-micellar solution. Reverse micelles comprising Aerosol-OT/iso-octane were taken as a model for dyeing in non-aqueous systems. The reactive dye was satisfactorily solubilised in the interior of the reverse micelle. Exhaustion of the reactive dye on cotton from the reverse micellar solution was excellent even in the absence of a dyeing auxiliary. Effective fixation was achieved by the use of a separate reverse-micellar solution containing a suitable alkali. It has also been shown that fixation can be successfully achieved using an alternative thermal process without the need for alkali.     

Correlation of solubility data of azo disperse dyes with the dye uptake of poly(ethylene terephthalate) fibres in supercritical carbon dioxide

Solubility data of disperse azo dyes in supercritical carbon dioxide are presented for dyeings of poly(ethylene terephthalate) fibres with CI Disperse Red 167:1, carried out at 200–300 bar and 80–120 °C, with varying amounts of adulterants. The same dyeings were also carried out in water for comparison. Scanning electron micrographs were taken of the dyes which show a growth of dye crystals during treatment in supercritical carbon dioxide. The paper reports that at 120 °C, melting of the pure dye CI Disperse Red 167:1 is observed. The presence of adulterants in the dye formulations help prevent agglomeration by acting as spacers between the dye molecules. Dyeings of PETP carried out under conditions of the highest solubility of the dye in supercritical carbon dioxide do not necessarily result in a very high dye uptake. This was shown by pressure- and temperature-dependent dyeing experiments of PETP in supercritical carbon dioxide.     

Relationship between the solubility of disperse dyes and the equilibrium dye adsorption in supercritical fluid dyeing

In order to understand the dyeing behaviour of synthetic fibres in supercritical carbon dioxide, the solubility of some disperse dyes in supercritical fluid, as well as the rate of dyeing and the equilibrium adsorption of these dyes, have been studied. Dye solubility was measured by a dynamic analytic method at a range of pressure (7.5–25 MPa) and temperature (50–145 °C). The apparent rate of dyeing was measured and the dyeing isotherm was obtained by plotting the equilibrium dye adsorption against the equilibrium dyebath concentration. Linear isotherms were obtained when poly(ethylene terephthalate) samples were dyed with the disperse dyes. The mechanism of dyeing using supercritical carbon dioxide was discussed by considering the solubility, the dyeing rate and the dyeing isotherm.     

Acid-dyeable acrylic fibres copolymerised with amino alkyl methacrylates for differential cross-dyeing

The equilibrium adsorption of acid dyes on acrylic fibres copolymerised with dimethyl amino ethyl methacrylate has been investigated. A typical characteristic of this type of fibre is its excellent stable dyeability over a wide pH range. This is due to the strong basicity of alkylamino groups in the copolymerised component, which makes it possible to dye the fibre thoroughly even in a weakly acidic dyebath using a normal dyeing processes of acrylic fibre with cationic dye. Consequently it is useful for differential cross-dyeing in a single dyebath.     

超临界二氧化碳染色的原理及研究进展

介绍了超临界二氧化碳染色具有染色时间短、匀染透染性好、染后不用还原清洗等优点,且整个染色过程中不会造成任何污染,解决了传统染色工艺使用大量的水造成浪费大,存在环境污染严重及资源消耗和有机溶剂染色的生态、成本、很难工业化应用的问题。同时介绍了超临界二氧化碳染色法的基本原理,对国内外超临界二氧化碳染色技术在合成纤维和天然纤维纺织品染色中的研究现状作了全面分析,并对其发展前景进行了展望。     

Investigations on the level dyeing of fabrics in supercritical carbon dioxide

The level dyeing of fabrics in supercritical carbon dioxide was investigated by employing an improved beam (a perforated pipe on which the knitted or woven fabric/warp is wound around). The effects of system temperature, pressure, dyeing time, a time ratio of fluid circulation to static dyeing (R_time), different fabric layers wrapped around the beam, and the species and chemical structures of dyestuffs on leveling properties and color strength of polyester and cotton fabrics were observed. The results show that the leveling properties and color strength of fabrics were improved on the new beam, as well as with a favorably increased system temperature, pressure, dyeing time, and a time ratio of fluid circulation to static dyeing; while the leveling property and color strength decreased with fabric layers on the beam under an identical condition. Highly leveling results were obtained on polyester and cotton fabrics with disperse and reactive disperse dyes involving different chemical structures.