Aqueous Dyeing Research Articles

Alkoxide-based solvent dyeing: a feasible strategy for pollution minimization and sustainable approach for the reactive dyeing of cellulosic materials

This study aimed to evaluate the feasibility of substituting the conventional inorganic alkalis (Na2CO3) with different organic alkoxide5s to explore the potential of replacing aqueous dyeing medium with environmentally friendly solvents like ethanol (EtOH). The study aimed to assess the dyeing characteristics, such as exhaustion, fixation, fastness qualities, physical properties, and environmental implications when EtOH and water were present, while also examining the impact of alkoxides. Time-gated Raman spectra provide insights into the allomorphic forms of cellulose-II after the alkoxide pretreatment, which significantly influences the overall reactivity of cellulose fibers and their dye absorption capabilities. Notably, organic alkoxide pretreated dyeing demonstrated improved color strength, exhaustion, and fixation efficiency compared to Na2CO3 pretreatment, as one of the work’s key findings. For instance, the conventional dyed fabric exhibits 3.4 times lower color strength than alkoxide-based (RR239 + C2H5ONa 3 g/L + EtOH) dyeing, showing substantial potential for upscaling at commercial level as it requires no chemical auxiliaries (such as NaCl and Na2CO3). Importantly, the alkoxide pretreatment does not significantly alter the physical, mechanical and fastness properties of the fabrics, which are comparable to both the pristine and aqueous dyed fabrics, as confirmed by scanning electron microscopy experiments. The effluent’s color intensity resulting from dyeing with C2H5ONa + EtOH (3 g/L) is approximately 24 times lower (250 Pt/Co) in comparison to the aqueous dyeing using 40 g/L of NaCl and 20 g/L of Na2CO3 in an aqueous medium (6154 Pt/Co). Apart from the color intensity, alkoxide pretreatment and EtOH-based dyeing drastically reduce the COD, BOD, TDS, TSS and total hardness values, which could have cost-saving implications for wastewater treatment plants (WWTPs).

Solvent-assisted salt-free reactive dyeing of cotton fabric

The objective of this study was to establish a solvent-assisted salt-free dyeing method for cotton fabric utilizing commercially available reactive dyes. In this study, the feasibility of substituting water as the dyeing medium with environmentally friendly solvents, specifically ethanol (EtOH), isopropyl alcohol (IPA), and propanol (PrOH), was investigated. Eight commercial reactive dyes, each possessing distinct chemical structures, were examined with various dyeing characteristics including exhaustion, fixation, and fastness properties, in the presence of various alcohols. However, solvent-assisted dyeing exhibited comparable or enhanced color strength (K/S) values, exhaustion, and fixation rates compared to conventional aqueous dyeing. For instance, the RR35 dye demonstrated a substantial increase in K/S values with PrOH, EtOH, and IPA, ranging from 115 to 369% improvement. The substitution of alcohol for water did not affect the wash, rub, and light-color fastness properties, as these properties remained consistently excellent. Solvent-assisted salt-free dyeing of cotton fabrics offers a promising solution to address the environmental impacts of traditional water-based dyeing methods by eliminating the requirement for water and salt. Overall, this study presents a solvent-assisted salt-free dyeing technique and contributes to the field by offering detailed insights into its mechanisms and performance. Our research has the potential to reduce water consumption, eliminate salt usage, and mitigate environmental pollution.

Organoclay-assisted disperse dyeing of polypropylene nanocomposite fabrics in supercritical carbon dioxide

Dyeing using supercritical carbon dioxide (SC-CO2) is carried out on the polypropylene (PP) nanocomposite fabrics with model disperse dye compared with their regular fabric at various dyeing temperatures and pressures. The results are compared with those obtained in aqueous dyeing method. The PP nanocompsite fabrics dyed in SC-CO2 medium exhibited higher colour strength (K/S) values compared with their PP regular fabric. The PP nanocompsite fabrics and their regular fabric dyed in SC-CO2 medium have higher K/S values than those dyed in aqueous medium. The color coordinates of all PP fabrics dyed in SC-CO2 and aqueous medium were positive with respect to a* and b* coordinates depending on the disperse red dye uptake. The PP nanocomposite fabrics dyed in SC-CO2 and aqueous medium exhibited higher antibacterial properties than their regular fabrics. All PP fabrics dyed in SC-CO2 and aqueous medium present very good washing, perspiration and light fastness.

Post‐modification of azo dyes using an α‐phenyl diazo ester for improving the colour fixation properties of polyurethane fibre

AbstractColour fastness of polyurethane fibre dyed with conventional disperse dyes is always poor owing to the insufficient affinity between fibres and dyes. Thus, three novel azo dyes containing an α‐phenyl diazo ester moiety were designed in this study. The dyes were synthesised through two‐step post‐modification of a hydroxylated azo benzene chromophore. All three dyes were characterised using proton and carbon nuclear magnetic resonance, high‐resolution mass spectrometry and infrared spectrometry. The ultraviolet‐visible absorption and thermal properties of the dyes were also studied. Fixation properties of these dyes on polyurethane fibre were examined using samples dyed using a non‐aqueous dyeing method. Practicality of these dyes, that is colour depth, fixation value, colour fastness and dye migration degree, was further verified on fibre dyed via an aqueous dyeing method. Finally, the mechanical properties of the dyed polyurethane fibre were explored.

Waterless Dyeing of Polyamide 6.6.

Waterless dyeing of polyamide 6.6 using scCO2 (supercritical carbon dioxide) was investigated. PA (polyamide) fibers can be dyed with various dyes, including disperse dyes. The conventional aqueous dyeing process uses large amounts of water and produces polluted water. Considering these environmental issues, waterless dyeing of fibers is a forefront issue, and utilization of supercritical carbon dioxide (scCO2) is a commercially viable technology for waterless dyeing. This study tested PA6.6 (polyamide 6.6) dyeing in scCO2 at 100 °C 220 bar pressure for 45 min. Color measurements and color fastness tests were performed, as well as tensile strength, scanning electron microscope (SEM) analysis, and Fourier transform infrared spectroscopy (FTIR) analysis. PA6.6 fabrics yielded higher K/S (color strength, the Kubelka-Munk equation) values with larger molecular weight dye and almost the same color strength with medium and small-sized dyes, demonstrating the ability of dyeing in a supercritical environment without water as a more environmentally friendly dyeing option compared to conventional dyeing.

The Influence of pH of Float on the Dyeability of Polyester Fabric

Disperse dyes are essentially non – ionic, exhibit poor solubility in water, and they can be used in the form of water dispersion. Polyester fibres are resistant to dilute aqueous acids and alkaline solutions and pH value does not provide a crucial impact on the dyeing mechanism; however, many disperse dyes undergo degradation if the pH is uncontrolled during aqueous dyeing. In order to minimize the possibility of dye hydrolysis, the dyeing is carried out in a slightly acidic medium, and pH is usually adjusted with acetic acid. In this work, the quantity of disperse dyes (Sinten Gelb P-5GL and Sinten Scharlach P-3GL) applied to polyester knitwear was investigated as a function of pH. The sorption capacity of polyester knitwear was monitored by using reflection curves and CIELab system, according to Swiss software Sandoz (based on spectrophotometry). The acetic acid was used for dyebath pH adjustment. The results showed that the maximum uptake of Sinten Gelb P-5GL and SintenScharlach P-3GL dyes by polyester knitwear occurred at pH 4.64 (0.2924%) and 6.20 (0.1860%), respectively. According to reflection curves in the range (max = 400-700 nm), the effect of pH on the sorption of Sinten Gelb P-5GL was more significant than one for Sinten Scharlach P-3GL, when concentration of dye is constant (0.4%). The CIELab values for three illuminants (daylight, light – bulb and incandescent) showed a significant dependence between pH float and hue and intensity of polyester knitwear dyeing with disperse dyes

Alkyl Polyglucoside (APG) Nonionic Surfactant-Based Reverse Micellar Dyeing of Cotton Fabric – A Study of Reactive Dyes with Different Functional Groups

ABSTRACT Reverse micellar dyeing of cotton woven fabrics with natural and biodegradable alkyl polyglucoside-based (APG-based) nonionic surfactant in decamethylcyclopentasiloxane (D5) non-aqueous medium with reactive dyes of different functional groups was investigated and compared with conventional aqueous water-based dyeing in terms of reflectance, color yield, levelness, CIE L*a*b* values, washing fastness and color fading properties. Experimental results have revealed that APG reverse micellar method can provide a higher color yield (K/Ssum value) and lower color reflectance (better dye uptake) than conventional water-based method, along with comparable washing fastness, leveling and color fading properties. Hetero-bifunctional reactive dyes can attain the highest color yield, followed by homo-bifunctional reactive dyes and mono-functional reactive dyes. Mono-functional reactive dyes and homo-bifunctional reactive dyes produce the best levelling properties with smallest levelness variation when compared with that of hetero-bifunctional reactive dyes in non-aqueous D5 dyeing medium.

Sustainable dyeing of wool yarn with Monascus pigments in non-aqueous medium

Wool fiber is commonly dyed with synthetic dyes in water medium, which may cause resource and environmental pressure arising from consumption of water and toxic chemicals. In this study, wool yarn was dyed with natural Monascus pigments in decamethylcyclopentasiloxane (D5) medium to minimize water consumption and effluent generation. Results indicated that K/S value of wool yarn dyed in D5 medium was higher than that of the samples dyed using the conventional aqueous dyeing methods. Moreover, wool yarn exhibited the highest color strength, good color fastness and bacteriostatic rate of 71.25% against Staphylococcus aureus when it was dyed under pH3 at 80 °C for 50 min. Meanwhile, XRD analysis revealed that crystal property of wool yarn did not change significantly when it was dyed in D5 solvent, and a similar phenomenon was observed in surface morphology by SEM analysis.

The roles of polymer relaxation phenomena, aqueous dye solubility and the physical properties of water in the mechanism of adsorption of a disperse dye on poly(ethylene terephthalate) fibres: Part 3 physical properties of water and water‐derived fibre properties

AbstractIn the absence of published information regarding the temperature dependency of water‐derived poly(ethylene terephthalate) fibre properties, the findings reported for the thermally regulated interactions between water and 100% amorphous poly(ethylene terephthalate) materials were interpreted from the perspective of the amorphous domains that reside within semi‐crystalline polyester textile fibres. This analysis suggests that the pronounced temperature dependent uptake of a commercial grade disperse dye on poly(ethylene terephthalate) fabric achieved during an aqueous dyeing process at temperatures between 30 and 130°C is the likely result of the combination of three separate, but inherently inter‐related, thermally activated phenomena, namely, polymer structural relaxation, in which polymer glass transition assumes a dominant role, dissolution of disperse dye in the aqueous dyebath, as well as various water–fibre interactions, in the guise of water sorption, water molecule diffusivity, water‐induced swelling and water‐induced plasticisation. Although thermally regulated macromolecular relaxation processes adopt the principal role in dye uptake, temperature dependent dye solubility and water‐derived fibre properties nevertheless likely provide crucially important supportive roles.

The roles of polymer relaxation phenomena, aqueous dye solubility and the physical properties of water in the mechanism of adsorption of a disperse dye on poly(ethylene terephthalate) fibres: Part 2 dye solubility

AbstractThe marked temperature‐dependent uptake of a commercial disperse dye on poly(ethylene terephthalate) fabric achieved during an aqueous high temperature dyeing process is the likely amalgamation of at least two separate, but intrinsically inter‐related, thermally activated processes, namely, poly(ethylene terephthalate) structural relaxations, as articulated in terms of polymer chain segmental mobility and available free volume, in which glass transition adopts a principal role, as well as disperse dye aqueous solubility. Both polymer relaxation times and disperse dye solubility therefore assume crucially important roles in the mechanism of adsorption of disperse dyes on poly(ethylene terephthalate) fibres.

Potential trade-off between water consumption and water quality: life cycle assessment of nonaqueous solvent dyeing

Fashion industry consumes over 60% of global fibers and attracts increasing attentions due to its environmentally polluting supply chain. In addition to natural fibers cultivation, wet processes of textile manufacturing are also important contributors to water-related impacts due to their large freshwater consumption and the production of chemicals containing wastewater. Despite of efforts made in improving efficiency of water use and wastewater treatment in textile industry, innovative ‘water-free’ technologies, such as nonaqueous dyeing technology using organic solvent, have been developed and demonstrated to reduce water consumption significantly. However, the potential impact on water quality by organic solvents induced in supply chain of this emerging technology remains unassessed, posing an unknown risk of its promotion. Hence, in the present study, a comprehensive life cycle assessment is applied to evaluate its full environmental impacts, including those on ecosystem and human health caused by decamethylcyclopentasiloxane (D5) as the solvent used. Further, the nonaqueous dyeing system is compared with traditional aqueous dyeing technology from both environmental and economic perspectives. Results indicate that nonaqueous dyeing system is advanced in most of environment categories except for abiotic depletion potential (ADP) and Ecotoxicity. However, scenarios analysis reveal that these findings are influenced by the loss fraction of D5 during the solvent recovery process. It is suggested that the loss fraction should be controlled below 2% o.w.f. for the nonaqueous dyeing technology to be advanced throughout all environmental categories. Nonaqueous D5 dyeing could reduce water consumption by 61.30%-79.95% and greenhouse gas emissions by 43.70% compared to the traditional system, delivering a promising contribution to China's 2060 carbon neutrality ambition. Sensitivity and uncertainty analyses are also conducted to investigate the effects of the key parameters (incl. inventory data and USEtox model inputs) and demonstrate the robustness of our assessment.

A salt-free and water-saving approach as a green alternative to conventional reactive dyeing of cotton

Aqueous reactive dyeing of cotton is considered to be environmentally unfriendly owing to its high consumption of water and salt as well as large discharge of wastewater. However, the industrial applications of current alternative dyeing technologies are difficult to realize due to different problems such as poor dyeing quality, environmental pollution and high cost. Herein, we developed a dyeing approach using hydrophobic deep eutectic solvent (HDES) composed of thymol from thyme leaves and menthol from Mentho haplocalvx Bing (two natural compounds with pharmacological function) to overcome the problems caused by reactive dyeing of cotton. HDES dyeing approach could achieve excellent dyeing properties of cotton by optimizing water content, pick-up and concentration of alkali solution. Dye fixation kinetics of HDES dyeing system was studied based on Lagergren pseudo-first-order and pseudo-second-order dynamics models, compared with aqueous dyeing system. The cotton fabrics dyed in Thy-Men system exhibited excellent levelness, satisfactory colorfastness and color strength without addition of salt. Furthermore, HDES can be reused for 5 cycles of dyeing and the dyed fabrics displayed consistently high color strength values. This dyeing approach provides substantial reduction in wastewater emission and consumption of freshwater and chemicals, which has considerable potential for promoting sustainable development of the textile industry.

Sustainable pilot scale disperse dyeing in a waterless silicone medium dyeing system for no discharge of wastewater

Clean dyeing technologies for polyester textiles, particularly waterless dyeing, have been studied extensively in recent decades. In the present work, a new waterless dyeing technology, the silicone medium dyeing, for polyester textiles had been investigated. The dyeing process of polyester textile in the silicone medium was optimized by determining the dyeing temperature, holding time, type and dosage of dye accelerator. The dye uptake of disperse dye and the fastness properties of the dyed polyester were equivalent to those of conventional water-bathed dyeing. After dyeing, polyester textile had a better color levelness. From the TGA and XRD results, it can be proved that silicone medium has no adverse effects on the fiber and can be used as a dyeing medium. The influence of the increase of halogen in the diazotized component on the affinity, dye uptake, diffusion coefficient, and other parameters was obtained by analyzing the dye uptake of C.I. Disperse Orange 44 and C.I. Disperse Yellow 163. These parameters formulate guidelines for the selection of disperse dyes for silicone medium dyeing system. To verify the feasibility of industrialization, pilot-scale dyeing was carried out. The results showed that, as compared to aqueous dyeing, higher colorfastness and better color levelness were obtained from silicone media. Therefore, this eco-friendly dyeing technology has considerable potential to become a mainstream dyeing method in the foreseeable future.

Solvent assisted dyeing of wool fibers with reactive dyes in a ternary solvent system for protecting fibers against damage

Severe effluent pollution and chemical damage to protein fibers generated from conventional aqueous dyeing process have stimulated interest in exploiting sustainable dyeing of wool. Herein, an ethanol (EtOH)-carbon tetrachloride (CCl4)-water (H2O) ternary solvent system was used as the dyeing medium to protect wool fibers from being damaged in the dyeing process. The wool fibers were firstly pretreated in an aqueous acid solution, followed by dyeing in the EtOH-CCl4-H2O (45:50:5) ternary solvent system with reactive dyes. The results indicated that the acid pretreatment solution could be reused for several times, the samples dyed in the EtOH-CCl4-H2O mixture with the investigated dyes showed higher K/S values compared to the conventional approach, implying the increased dye utilization and decreased effluents discharge were realized. Furthermore, acceptable permeability, good colorfastness, and satisfactory leveling properties of the dyed samples were achieved using the developed method. Additionally, the solvent-assisted dyed samples showed improved mechanical properties compared with the conventionally dyed samples. The dyeing mechanisms of wool fibers in the EtOH-CCl4-H2O mixture were illustrated in detail. The proposed dyeing technology consumes fewer energy, freshwater, and chemicals compared with the conventional wool dyeing method. Future work will principally concentrate on the reuse of the dye-contaminated EtOH-CCl4-H2O mixture.

Thermodynamic properties of cotton dyeing with indigo dyes in non-aqueous media of liquid paraffin and D5

On the basis of investigation into the dyeing equilibrium of cotton fibers with indigo dyes in decamethylcyclopentasiloxane (D5), liquid paraffin and water, the thermodynamic properties of cotton dyeing with indigo dyes in non-aqueous medium systems were studied in comparison with aqueous dyeing. The main works involved are as follows: firstly, the adsorption isotherms were created; then, the three theoretical adsorption models of Nernst, Langmuir and Freundlich were used to fit the adsorption isotherms created; finally, the thermodynamic parameters were calculated. The results showed that the adsorption isotherms were all in line with the Freundlich model. The order of dyeing affinity was in the sequence: liquid paraffin > D5 > water. The dyeing entropy in the three media showed positive values, which is mainly attributed to the adsorption of both indigo-leuco and water onto cotton fibers, thus reducing the ice-like structure formed among the water molecules in the dyeing system and the hydrophobic bonding structure formed among the non-aqueous medium molecules, then leading to an increase in the system disorder. The dyeing heat in the three media also showed positive values, due mainly to the absorption of thermal energy to “melt” the ice-like structure and to “break” the hydrophobic bonding structure. These dyeing thermodynamic properties are conducive to understanding and interpreting the dyeing performance and behavior of indigo dyes in non-aqueous dyeing systems.

Sustainable dyeing of cotton fabric with reactive dye in silicone oil emulsion for improving dye uptake and reducing wastewater

From sustainable chemistry and engineering perspectives, water and energy consumption are arguably the main issues in the textile industry. Thus, a silicone reverse emulsion dyeing system is developed to dye cellulosic textile with reactive dye. When the amount of dye is the same, the color depth of dyed cotton fiber is 13.82 and the fixation of dye is 87.76% in the silicone reverse emulsion dyeing system. In traditional water-based dyeing system, the color depth of dyed cotton fiber and the fixation of dye is only 9.31, 56.63% respectively. The silicone reverse emulsion dyeing technology does not consumes salts, but it can improve the dye fixation by 31.13%, and decreases the dye discharge by 72.41%. For the hydrolysis of bifunctional reactive dye, the main hydrolysis reaction is the individual hydrolysis of monochlorotriazine or vinyl sulfone at the prophase of hydrolysis. After 30 min, the additional β-hydroxyethyl sulfone and hydroxyl triazine dye are hydrolyzed to dihydroxyl dye. To confirm the hydrolytic reaction energy of dye in different dyeing system, the optimization of molecular structure, the hydrolysis reaction gap and the distribution of electron density on the dye were investigated using density functional theory. The hydrolytic reaction energy gap of bifunctional reactive dye is higher in silicone reverse emulsion dyeing system than that in traditional aqueous dyeing system, resulting the hydrolysis of dye is difficult in silicone oil emulsion dyeing system. The electron density is distributed almost entirely on the carbon–carbon double bond and triazine group in the HOMO of the dye, resulting in the LUMO of dyes can attacked by HOMO of hydroxyl anion. These successful investigations of the dyeing performance and the hydrolysis mechanism of dye explain that reactive dye can keep a long reactivity to fiber and effectively reduce the number of washing times, which greatly reduces the discharge of dyeing waste water.

Solvent assisted dyeing of silk fabric using glycerine based eutectic solvent as a swelling agent

PurposeDyeing of silk fabric was studied to increase dye uptake using eco-friendly glycerine based eutectic solvent (GES), which acts as a swelling agent.Design/methodology/approachThe swelling behaviour of silk fabric in GES was analyzed using three-dimensional laser scanning microscope. Dyeing parameters such as time, temperature and GES concentration were optimized using design of experiments.FindingsIn total, 5.34 F-value and 0.0014 p-value of ANOVA represent that the model is significant. An optimized GES assisted dyeing was carried out with two different classes of dyes such as Acid Blue 281 and Acid Red 151 and further compared with that of conventional aqueous dyeing method.Originality/valueAt 70°C, silk fabric achieves desired colour strength after 35 min of dyeing (10 min lesser than conventional) using GES assisted dyeing method. % Dye exhaustion of GES assisted dye bath was carried out and found to be very good. Fastness properties such as washing, light and rubbing fastness of conventional and GES assisted dyed silk fabric showed comparable results.

Effluent-free deep dyeing of cotton fabric with cacao husk extracts using the Taguchi optimization method

Textile dyehouses are under scrutiny because they discharge colored and hazardous effluents to waterways. There is a need to develop an alternative dyeing system that does not produce any hazardous effluent. The waterless dyeing method could be a viable eco-friendly alternative to the traditional aqueous dyeing method. In this work, cacao husk extracts were used as a natural dye in the decamethylcyclopentasiloxane (D5) medium for the dyeing of cotton fabric, and subsequently, the dyed cotton was treated by a fixation treatment with a cationic dye-fixing agent in the D5 medium. The cotton fabric dyed with cacao husk extracts exhaustion in the waterless D5 medium exhibited better exhaustion, fixation rate, color strength (K/S), and colorfastness to washing and rubbing compared to the fabric dyed with the same extracts using the conventional aqueous dyeing and dye-fixing methods. The dye exhaustion percentage and the dye fixation rate were 95.6% and 94.8% in the D5 medium respectively, which is significantly higher in comparison to a 48.2% dye exhaustion percentage and a 35.3% dye fixation rate in the conventional water medium. An orthogonal array design (L9) was adopted to optimize the dyeing conditions with respect to exhaustion percentage. The results indicated that the dyebath temperature was the most important factor for achieving the optimal dye exhaustion, and dyeing time also showed considerable effects. Linear regression was used to predict the exhaustion percentage, and the resulting p value of 0.000 demonstrated that a strong coefficient was proven among all selected factors. This study has demonstrated that dyeing of cotton fabric with cacao husk extracts in the D5 dyeing system can be a viable method for the textile industry with minimal environmental pollution.

Sustainable dyeing of nylon with disperse dyes in Decamethylcyclopentasiloxane waterless dyeing system

Because of the prevailing issue of water scarcity, the application of non-aqueous media Decamethylcyclopentasiloxane (D5) was employed in the chemical fiber dyeing and washing process. Confocal laser scanning microscope (CLSM) and X-ray photoelectron spectroscopy (XPS) analysis have been carried out to analyze the penetration of D5 into the interior of nylon fiber and its distribution in fiber cross-section. The solubility of pure disperse dye in D5 has been measured to check the feasibility of dispersing agent exclusion from dyeing formulation. For developing the solvent dyeing and washing process for nylon, nylon fabric was dyed with pure disperse dyes in D5 solvent and washed with D5 without any process auxiliaries. Findings from CLSM and XPS spectrum showed that D5 can diffuse into the nylon fabric surface with and without the addition of accelerant. And accelerant doesn’t affect D5’s ability to penetrate and uniform distribution within the fiber structure. As compared to aqueous dyeing, the 30 and 43 percent increase in K/S was achieved for azo and anthraquinone dyes by using D5 as dyeing media. Furthermore, more than 99 percent solvent can be recycled or recovered. The level dyeing with commercial dyes under conventional dyeing conditions in D5 solvent dyeing media prove the commercial feasibility of this dyeing technology.

A water/cottonseed oil bath with controllable dye sorption for high dyeing quality and minimum discharges

Abstract We developed a clean reactive dyeing system for industrialization by controlled demulsification of the dyeing medium containing cottonseed oil. Low dye fixation and high pollution are the major problems of conventional aqueous reactive dyeing. Current alternative dyeing technologies have their deficiencies such as undesired dyeing quality and toxic discharges. Semi-stable emulsion dyeing could achieve high levelness and fixation of dyes by adjusting the demulsification speed of dyeing medium and water content in the system on a pilot scale. Compared to aqueous dyeing, up to 47% dyes could be saved to obtain the same shade in semi-stable emulsion dyeing. Dyeing levelness of emulsion dyeing has no significant difference from that of aqueous dyeing. Dye discharge using the semi-stable emulsion system was reduced by 90%. Discharges of salt and dispersing agents were eliminated. More than 99.8% of cottonseed oil could be recycled.