Influence of additive organic base on dyeing of cotton fabric under supercritical carbon dioxide using fluorotriazine reactive disperse dye and investigation of optimal dyeing conditions

https://doi.org/10.1016/j.supflu.2021.105243Get rights and content

Highlights

  • A single coloration of cotton with fluorotriazine-based dye was observed.

  • Influence of the additive organic basis on the reactions was described.

  • Optimal dyeing process was clarified in 2 h with α-picoline at 120 °C.

  • Dyed cotton color fastness to washing and rubbing were rated at 4–5.

Abstract

This paper demonstrates the impact of an organic base on dyeing of cotton fabric using a fluorotriazine-based reactive disperse dye under waterless dyeing conditions with supercritical carbon dioxide (scCO2). The cotton fabric was dyed without pre-treatment. The system parameters, including temperature, pressure, time, and dye concentration, were examined. The systematic variation in the parameters indicated that the optimal coloration was achieved by adding 300 mM of α-picoline as an alkali at 120 °C and 25 MPa under scCO2. The dye structure was determined using infrared and nuclear magnetic resonance spectral data, showed a good agreement with the structure proposed. The morphological structure was partially identical with no damage to the cotton, as determined using scanning electron microscopy. The results indicated that fluorotriazine-based dye has a high coloring behavior, with the color strength, leveling properties, and staining fastness rated at 4–5 in terms of a dyeing medium with α-picoline.

Introduction

The conventional aqueous textile procedures are among the major environmental pollution sources due to the discharge of a tremendous amount of wastewater, with over 24.0 billion tons of effluents discharged within the environment annually [1]. Concerns have arisen regarding primary pollution sources related to dyeing cotton fabrics, which include adding an enormous amount of water-soluble polar dyes such as reactive dyes, various types of dissolved electrolytes, and auxiliaries during the coloration process. This strategy causes a dilemma in terms of the released effluents into the environment, which is hindering the possibility of an eco-friendly textile industry [2].

A sustainable and eco-friendly textile dyeing based on supercritical carbon dioxide (scCO2) fluid could potentially resolve pollution issues in the textile industry [3], [4]. The fundamental role of this novel technology involves shifting the technological processes of dyeing cotton fabrics to a waterless, non-toxic, and recyclable process for finishing procedures for fabrics. In short, the application of the scCO2 technology could reduce waste and costs involved in the entire dyeing cycle compared with those of traditional methods [5], [6].

In fact, the dyeing of manufactured textiles using scCO2 has returned encouraging results, which are attributed to the low viscosity of scCO2, with the dissolved dyes readily penetrating into the pores and capillaries of synthetic fibers [7], [8], [9], [10], [11], [12], [13]. Certain studies have even satisfied the conditions of industrial dyeing processing. However, to date, scCO2-based dyeing results for cotton fibers have been largely poor. Numerous approaches have been developed to overcome the difficulties of the scCO2-based dyeing method for cotton fabrics, which are related to the fact that natural fibers have discriminatory reaction sites in their structure that are characterized by various hydrophilic (–OH) groups. Meanwhile, the hydrophobic medium of scCO2 makes it challenging to swell the cotton fabrics [14].

In recent years, much of the relevant research has focused on resolving difficulties of scCO2-based dyeing systems in relation to cotton fabrics [15], [16], and the various strategies used can be summarized as follows: (1) investigating the behavior of the hydrophobic tendency of cotton fabric through chemical alterations, with Ozcan et al. dyeing cotton modified with benzoyl chloride using disperse dyes in scCO2 to return good color yields [17]; (2) facilitating the dissolution of the dye with the cotton fabrics using auxiliary agents, with Beltrame et al. [18] attempting to dye cotton fabrics using polyethylene glycol (PEG) and finding that the dye uptake was significantly increased with good fastness; and (3) developing scCO2-soluble non-polar reactive disperse dyes, which have reactive groups that bind to the disperse dye to enable reaction with the cotton fibers by forming specific chemical bonds [19].

Further observations have indicated that since scCO2-based technology presents a waterless technique that does not involve the use of water during the dyeing, the commercial requirements have not yet been met in terms of the fixing of normal dyes, which means that using reactive disperse dyes consisting largely of fluorotriazine groups as a bridge group plays an important role in the coloration properties in terms of dye uptake, penetration, and reactivity during the process for dyeing cotton fabrics [20], [21]. Fluorotriazines are also believed to be more fabric-reactive than chlorotriazines, largely because, in chemical terms, in mono-, di-, and tri-fluorotriazine, the fluorine is replaced more easily by water or alcohol than by primary or secondary amines [22]. However, despite the intense reactivity, the low selectiveness of fluorotriazine has restricted its application in reactive water cotton dyeing. In short, the fluoride atom of the reactive triazine group will be immediately hydrolyzed and subsequently become inactive during processes of water dyeing and cotton finishing [23], [24], [25].

Furthermore, although cotton fiber is commonly regarded as one of the most important natural fibers, with the scCO2-based dyeing process, serious issues remain in terms of the industrial process. Here, one major challenge relates to how the requirements of scCO2 are insufficient in terms of dye absorption, penetration, and color yield, especially with dark shades. Meanwhile, the efficiency of dyeing using reactionary dispersion presents another issue for cotton fiber non-polar scCO2 processes due to the higher crystallinity and polarity of the cotton fiber [22]. In addition, the construction of medium-sized industrial equipment for scCO2 dyeing differs from that of the traditional chemical plant. Nonetheless, the dyeing apparatus plays a crucial role in the development of the supercritical CO2 dyeing technology, with deficiencies in terms of dyeing deviation and the uneven color of the dyed cotton fabrics often demonstrated [25], [26], [27].

To avoid issues related to this reaction, various types of organic bases have been applied to the dyeing system or to the additional process steps. Here, several studies have demonstrated the effect of different organic bases in aqueous solutions, with Ahmed et al. reporting the conventional dyeing of cotton using reactive dyes with organic electrolytes based on acetate anion CH3COO (tetrasodium edetate as the exhausting and swelling agent) [28]. Meanwhile, Chen et al. explored the dyeing of cotton using vinyl sulfone dyes with a mixture of non-nucleophilic solvents in scCO2 [29]. Here, the re-use of all processing solvents and apparatus, including the dyeing and swelling baths, was achieved, making the process completely recyclable and waste-free.

In this regard, disperse reactive dyes with an appropriate chemical structure under optimum conditions are the key to enhancing the dyeing and finishing of cellulosic fabrics using the waterless and green technology incorporating scCO2, which helps to limit the steps involved in the dyeing process. In fact, a novel, greener procedure for dyeing cotton fabrics using fluorotriazine reactive disperse dye with scCO2 presents a potential solution for achieving good coloration properties in terms of color depth, dyeing uniformity, and color fastness.

Section snippets

Materials and chemicals

A 100% bleached plain-weave cotton fabric was supplied by Shikisenshe Co., Ltd., and commercial reactive disperse blue dye based on fluorotriazine was obtained from Mitsubishi Chemical Industries Corporation. Various organic bases, including 3-amino pyridine; 4-amino pyridine; 2-amino pyridine; 1,4-phenylenediamine; pyridine (Tokyo Chemical Industry Co., Ltd.); α–picoline; β-picoline (Kanto Chemical Co., Inc.); and γ-picoline; and 2,6-lutidine (Fujifilm Wako Pure Chemical Corporation) was also

Spectral analysis

The analysis of the dye indicated that a compound was obtained in the form of blue crystals (598.23–613.5 UV spectra). The compound shown in Fig. 2, i.e., 1,5-diamino-2-(4-[4-[dibutylamino]−6-fluoro-1,3,5-triazin-2-yl] oxy] phenyl)-4,8 dihydroxyanthracene-9,10-dione, was verified on the basis of its correct analytical and spectral data. Meanwhile, the determination of the structure of the blue dye was based on the values of the elemental analysis and the relevant spectral data (IR, 1H NMR, and

Fastness properties

A relatively good coplanarity of the dye molecules was achieved for the chemical structure under the optimum scCO2 conditions, i.e., a constant temperature of 120 °C, a dyeing time of 2 h, a dye concentration of 3% o.w.f., pressure of 25 MPa, and an α-picoline concentration of 300 mM. Based on the different fastness experiments, it was clear that the color fastness plays a significant role in the dyeing efficiency in terms of K/S.

Table 2 presents the color fastness properties (washing and

Conclusion

The aim of this study was to achieve a greener, eco-friendly process for dyeing cotton fabrics using the most recent technology for the one-step dyeing of fabrics using scCO2 and a new fluorotriazine-based reactive disperse dye. Given the good saturation and dye uptake (K/S), the color fastness values of 5 for both washing and rubbing, and the good mechanical properties, the optimum values for the dyeing system for cotton fabrics using scCO2 were found to be a temperature of 120 °C, a dyeing

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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