Air gap spinning of a cellulose solution in [DBNH][OAc] ionic liquid with a novel vertically arranged spinning bath to simulate a closed loop operation in the Ioncell® process

Chamseddine Guizani,Kaniz Moriam,Sami Rantasalo,Daisuke Sawada,Sherif Elsayed,Sauli Larkiala,Michael Hummel,Herbert Sixta

doi:10.1002/app.49787

Abstract

AbstractA novel, small‐volume vertically arranged spin bath was successfully developed for an air gap lyocell‐type spinning process. A maximum regeneration bath length with a minimum free volume characterizes the concept of the new spin bath. Using the ionic liquid (IL) 1,5‐diazabicyclo[4.3.0]non‐5‐enium acetate [DBNH][OAc], the spin bath showed very good spinning performances of IL‐cellulose dopes at high draw ratios and spinning duration for single filament spinning experiments. Using this new device, it was possible to get a step further in the optimization of the Ioncell® process and simulate a process closed loop operation by performing single filament spinning in IL/H2O mixtures. Good dope spinnability and preserved fibers mechanical properties were achieved in a coagulation bath containing up to 30 wt% IL. It is only at 45 wt% of IL in the bath that the spinnability and fibers mechanical properties started to deteriorate. The fibers fibrillar structure was less pronounced in IL‐containing spinning bath in comparison to a pure water bath. However, their crystallinity after washing was preserved regardless of the spinning bath composition. The results presented in this work have a high relevance to the upscaling of emerging IL‐based cellulose dissolution and spinning processes.

Highlights

Ioncell® is a new lyocell-type process for the production of man-made cellulosic fibers based on the direct dissolution of a cellulose substrate, preferably a dissolving pulp, in an ionic liquid (IL), air gap spinning of the solution in a water bath, and a subsequent solvent recovery step in which the IL, H2O and impurities generated are separated
A novel, small-volume vertically arranged spin bath was successfully developed for an air gap lyocell-type spinning process
The change of cellulose regeneration kinetics as a function of the solvent concentration in the coagulation liquid was studied for different cellulose solvent systems, and showed the dependence of the regeneration rate on the coagulation liquid composition[9,10,11] apart from results on diffusivity measurements for H2O and IL and insights on coagulation mechanisms,[7,12,13,14,15] we could not find data in the literature on cellulose dope spinning in H2O/IL mixtures, though they are critical for a successful scale up of an IL-based cellulose fiber spinning process

Summary

Introduction

Ioncell® is a new lyocell-type process for the production of man-made cellulosic fibers based on the direct dissolution of a cellulose substrate, preferably a dissolving pulp, in an ionic liquid (IL), air gap spinning of the solution (spinning dope) in a water bath, and a subsequent solvent recovery step in which the IL, H2O and impurities generated are separated. A gram-scale, monofilament spinning device used in our laboratory experienced some limitations regarding spinning behavior and comparability with the larger multifilament spinning systems.[17,18] The existing coagulation bath was identified as the main cause of the impaired spinning behavior: uncontrolled temperature and no fluid circulation, leading to poor mass transfer conditions. This coagulation bath had a volume of 24 L, which is already quite high for conducting spinning experiments with significant amount of IL in the coagulation liquid. Turbulences in the spinning channel would be unavoidable beyond a certain flowrate limit, and will be detrimental to the spinning operation

Methods

Results

Conclusion