Synthesis of a Novel Disperse Reactive Dye Involving a Versatile Bridge Group for the Sustainable Coloration of Natural Fibers in Supercritical Carbon Dioxide

Abstract

Disperse reactive dyes with appropriate chemical structure are key for the coloration of natural fibers in the water‐free environmentally friendly medium of supercritical carbon dioxide with various advantages. The objective of this work is to design and synthesize a novel anthraquinonoid disperse reactive dye involving a versatile bridge group to improve the coloration properties of the dye in supercritical carbon dioxide. Cross‐coupling condensation based on an Ullmann reaction between N‐phenylethylenediamine and 1‐chloroanthraquinone in a ligand‐free system is investigated by optimizing the synthesis parameters. Notable influences are observed from the dosages of N,N‐dimethyl formamide and potassium hydroxide, as well as the system temperature and reaction duration, on the isolated yield of the dye precursor. An optimized process is also recommended for synthesizing the designed novel dye. Then, the chemical structure, color characteristics, and coloration properties of the obtained dye are further investigated and successfully characterized by utilizing Fourier‐transform infrared analysis, 1H and 13C nuclear magnetic resonance spectroscopy, UV–vis absorption spectroscopy, elemental analysis, and liquid chromatography‐mass spectrometry. Additionally, practical coloration experiments are performed with cotton, silk, and wool in a supercritical carbon dioxide medium.

Recent advances in supercritical fluid dyeing

“…The choice of modifying disperse dyes with appropriate reactive groups able to bind with the textiles functionalities seems to be the winning strategy, which has allowed F values of up to 98%-100% to be obtained. 65,67,70 However, the intensity of coloration is still much lower with respect to PET and other synthetic polymers. Future investigations could probably be directed at deepening the chemistry of coloration in the supercritical environment.…”

“…It is evident that the coloration of hydrophilic materials in the non-polar supercritical environment suffers from a lack of solvent swelling of the fibres, which is confirmed by the fact that many researchers are trying to make the technology work by using pretreatments or other wet processes. 57,[64][65][66][67]77,79,80 This is the downside of SFD. As conventional aqueous dyeing of PET requires the use of auxiliaries to promote dye diffusion into the hydrophobic polymer, the dyeing of hydrophilic fibres in supercritical carbon dioxide probably cannot do without polar carriers or co-solvents.…”

“…Coloration efficiency is generally quantified by means of the K/S and the fixation efficiency (F). 57,[63][64][65][66][67][68][69][70] Two K/S values are generally evaluated: the first one on the "just-dyed" samples, the second after treating the textiles with an appropriate high temperature solvent extraction to remove the unfixed dye. The data reported in Table 4 refer to the after-extraction K/S.…”

“…On the contrary, very recent tests with anthraquinone-structured chlorotriazine dyes have revealed that better coloration and F could be obtained on wool and silk rather than cotton. Two series of dyes were prepared by the same research group in two different studies 65,66 to dye cotton, wool and silk in the presence of small amounts of acetone 65 or of an unspecified special dyeing auxiliary. 66 With respect to azo-structured chlorotriazine dyes, much lower K/S values were obtained for all types of fibres.…”

“…Reaction of dichlorotriazine dyes with (A) amino or (B) hydroxyl groups of proteinaceous and cellulosic textiles 65 …”