Cellulose regeneration and spinnability from ionic liquids

Abstract

Ionic liquid solutions of cellulose or dopes can be spun into Lyocell-type textile fibers by dry-jet wet spinning. An extruded dope is drawn over an air gap into water, where the water hydrates the ionic liquid and cellulose is regenerated. Spinnability studies have concentrated on the deformation and failure modes in the air gap and thus the rheology of the unhydrated spinning dope. Herein, a breach in the bath, another failure mode, is discussed. Dopes are prepared from the good spinning solvents NMMO·H2O and [DBNH]OAc and the poor spinning solvents [emim]OAc and [TMGH]OAc. The diffusion constants for water diffusing inwards and for ionic liquid diffusing outwards the emerging filament are measured offline. The resiliences and strengths of cellulose-ionic liquid solutions with different hydration stoichiometries are measured by means of rheometry. By calculating the diffusion dynamics, the resilience distribution of the forming filament is simulated. Gel strength distribution accounts for the tendency of [emim]OAc dopes to undergo a telescope-type breach, whereas the gelatinous solution state of [TMGH]OAc dopes accounts for their poor spinnability.

Renewable High‐Performance Fibers from the Chemical Recycling of Cotton Waste Utilizing an Ionic Liquid

“…In am atured traditional recycled textile market, there is very little opportunity to make value-added products. [31] The next concern with these ILs is the severe degradation of cellulose, especially at elevated temperatures. To date, this is not possible with conventional viscosea nd Lyocell techniques.…”

“…[29][30] However,p reviouss tudies focused almost exclusively on the use of imidazolium-based ILs that lack certain viscoelastic properties for the further processing of the respective cellulose solutionsi nto high-performance fibers. [31] The next concern with these ILs is the severe degradation of cellulose, especially at elevated temperatures. [32] This group of ILs is not inert towards cellulose.…”

Identifying breach mechanism during air‐gap spinning of lignin–cellulose ionic‐liquid solutions

“…However, the experimental work only covered solutions up to 8 wt % cellulose and all at room temperature. Furthermore, Hauru et al . presented the possible draw ratio for cellulose in different solvents but scarcely commented the mechanisms causing the breaches .…”

“…However, the experimental work only covered solutions up to 8 wt % cellulose and all at room temperature. Furthermore, Hauru et al 25 presented the possible draw ratio for cellulose in different solvents but scarcely commented the mechanisms causing the breaches. 25 The screening of a broader range of temperatures, and consequently viscosities, has, in many cases, been hindered by the high melting points and low degradation points of the solvent and/or polymer.…”

“…Furthermore, Hauru et al 25 presented the possible draw ratio for cellulose in different solvents but scarcely commented the mechanisms causing the breaches. 25 The screening of a broader range of temperatures, and consequently viscosities, has, in many cases, been hindered by the high melting points and low degradation points of the solvent and/or polymer. For example, N-methylmorpholine-N-oxide (NMMO), the solvent used for processing cellulose in the industrial Lyocell process, can only be used within the range of 80-120 C. 26 Consequently, there is a need to comprehensively investigate the link between the rheology of the solution and the breach mechanism during air-gap spinning.…”