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The direct dissolution of cellulose offers a pathway to production of regenerated textile fibers. However, fiber production in the Lyocell process requires a high recyclability of the solvent. Some compounds from the class of ionic liquids (IL) may have higher dissolving capacities together with a higher thermal stability than the conventional N‐methylmorpholin‐N‐oxide (NMMO), which makes them more valuable in an industrial process. A promising representative of such an advanced solvent for Lyocell process, 7‐Methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene acetate ([MTBDH][AcO]) was investigated in this study. A series of 21 consecutive cellulose dissolving and spinning trials via dry‐jet wet spinning was conducted with the same batch of solvent. In the spinning trials, the cellulose was regenerated into water consisting spinning bath. The solvent was recycled by removing the water from the spin bath via distillation in reduced pressure. Due these drastic changes in the water content of the IL during the whole process, the hydrolytic stability is an important aspect to assess the recyclability of the IL and viability of the whole process. The chemical composition of the IL was monitored by means of NMR spectroscopy. Although there was an increase of hydrolysis level of the solvent, cellulose could be dissolved constantly and spun to obtain staple fibers. The spinning behavior deteriorated slowly along the additional cycles, along with a measured increase in zero‐shear viscosity of the spinning dope. Nevertheless, the physical properties of the obtained fibers were barely influenced by the changes of the ionic liquid. [ABSTRACT FROM AUTHOR]

Cotton fibre dissolution has been investigated using ionic liquids having a functionalized imidazolium cation. Two ionic liquids, 3-butyric acid-1-methyl imidazolium chloride [HOOC4MIM][Cl] (IL-acid) and 3-N,N-diethyl-butyramide-1-methyl imidazolium chloride [(Et)2NOC4MIM][Cl] (IL-amide), were synthesized by passing both through the intermediate 1-(3-Ethoxycarbonyl-propyl)-1-methyl imidazolium bromide. Their chemical structures were then confirmed using NMR and FTIR. 5 wt% cotton fibers have been completely dissolved in both synthesized ionic liquids in 3 h at room temperature. The regenerated cellulose with water, as an anti-solvent, was characterized using XRD, FTIR, TGA, and degree of polymerization (DP) methods. The FTIR and XRD results showed that no other chemical reaction occurred by both synthesized ILs other than the breakage of hydrogen bonds during the dissolution and regeneration processes. In addition, the regenerated cellulose had a reduced crystallinity and a structural transition from cellulose I to cellulose II. TGA results confirmed the low crystallinity of regenerated cellulose by demonstrating its low thermal stability compared to cotton fibers. Furthermore, the DP of cotton fibers was reduced from 805 ± 15 to 737 ± 12 and 765 ± 10 after regeneration from IL-acid and IL-amide, respectively, confirming partial cellulose network degradation. The IL-acid has an oily appearance and a viscosity (44 ± 5 mPa.s at 25 °C), allowing it to dissolve 14.5 wt% cotton fibers at 25 °C, IL-amide can only dissolve 5 wt% in 5 h at 25 °C due to its viscous nature. These results imply that the produced ionic liquids can be considered as competitive solvents for dissolving cellulose. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) and deep eutectic solvents (DESs) are the two most widely used neoteric solvents. Recently, our group described how the simple addition of acetic acid (AcOH) to 1-Ethyl-3-methylimidazolium chloride (EMIMCl) could promote the transition from the original IL to an eutectic mixture of EMIMCl and AcOH. Herein, we studied how cellulose regeneration and EMIMCl recovery from EMIMCl solutions of cellulose could be benefited by the significant differences existing between EMIMCl- and EMIMCl·AcOH-based mixtures and the easy switching from one to the other. Finally, we also demonstrated that the transition could also be accomplished by addition of acetic anhydride and water so that the process could be eventually useful for the achievement of highly acetylated cellulose. [ABSTRACT FROM AUTHOR]