Regeneration of Cellulose from a Switchable Ionic Liquid: Toward More Sustainable Cellulose Fibers

Abstract

A CO2 switchable solvent system is investigated to find an environmentally friendlier way to produce man‐made cellulose fibers. Cellulose solutions with concentrations from 2 wt% to 8 wt%, based on derivative and non‐derivative dissolution approaches, are investigated. Three different switchable solvent systems are tested. After accessing the stability of the produced cellulose solutions, their regeneration is investigated using different alcoholic coagulation media. In order to find a suitable coagulation medium and stable cellulose solution, a dissolution–regeneration cycle is investigated, while trying to minimize the amount of waste by recovering the employed solvents. The process is optimized and the resulting fibers are characterized by infrared (IR) spectroscopy, optical microscopy, as well as scanning electron microscopy.

Structure and Properties of Regenerated Cellulose Fibers Based on Dissolution of Cellulose in a CO2 Switchable Solvent

“…The key factor for the regulation of the physic process is the double diffusion of the co-solvent and the nonsolvent between the coagulation bath and the spinning dope, which can be simply controlled by the temperature and the composition of the coagulation bath and the residence time of the gel-state fiber in the coagulation bath. As a nonsolvent for cellulose, H 2 O was widely used as a coagulation bath for the regeneration of cellulose in wet spinning for many cellulose dissolution systems, such as viscose rayon, NaOH/urea aqueous solution, ,, ionic liquid, , and NMMO. ,, In the case of the CO 2 switchable solvent, although previous studies have used not only H 2 O but also alcohol as a coagulation bath for the regeneration of cellulose for the preparation of cellulose film and fiber, the regenerated cellulose films prepared from alcohol were amorphous, which was not favorable for the preparation of cellulose fiber with good mechanical properties. Therefore, we started our exploration by employing H 2 O as the coagulation bath for wet spinning of cellulose based on the CO 2 switchable solvent.…”

“…It has been demonstrated in previous studies that DMSO and DBU can be recovered after regeneration of cellulose. ,, Therefore, we also designed and performed solvent recovery after wet spinning (Figure S4). Our results showed that the recovery yields of DMSO and DBU were 86.6 and 42.4%, respectively.…”

“…31 These studies demonstrated its great feasibility for the dissolution, derivatization, and processing of cellulose. 32 As one of the most widely used forms of regenerated cellulose materials, fibers have not yet been well prepared and studied using this system, 33 which is of great interest and necessity. Herein, a systematic study was carried out for the preparation of regenerated cellulose fibers via wet spinning with the green viscose system.…”

Closing the Carbon Loop in the Circular Plastics Economy

“…In recent years, progress has been made by Meier, who introduced a more sustainable process for esterification of cellulose in a switchable 1,8diazabicyclo[5.4.0]undec-7-en (DBU)/CO 2 solvent system that holds promise for the development and processing of advanced cellulose-based plastics. [165][166][167][168][169][170][171][172][173] Tough and transparent cellulose nanopaper with high porosity was derived from aqueous dispersions of cellulose nanofibrils. [174][175][176][177][178][179] Advances in nanofibrillated cellulose production and its potential applications, ranging from nanopaper to nanocomposites, coatings, and food packaging, have been addressed by several reviews.…”

Homogeneous cyanoethylation of cellulose with acrylonitrile in a CO2 switchable solvent

“…As a result, the dissolution of cellulose is achieved. Thereafter, a series of studies showed that this system can be used for the homogeneous chemical modification of cellulose for the synthesis of cellulose esters 33,34 and cellulose carbonates, [35][36][37] and for the processing of cellulose to prepare regenerated cellulose films, 38,39 fibers, 40,41 and aerogels. 42 Interestingly, in our previous study, we found that this system can be considered as "organic viscose", because of its similarity to the classical viscose sytem.…”