Semi-continuous, industrial-like production of transparent cellulose films by means of the Lyocell-type Ioncell® process

Abstract

A semi-continuous and industrial-like process to produce regenerated cellulose films, based on the Ioncell® technology, is demonstrated. The demand for commercial films, mainly fossil-based, is immense and expected to triple by 2060. This overconsumption leads to drawbacks like fossil reserves depletion and environmental pollution. Therefore, finding sustainable alternative processes compatible with existing industrial operations to produce films from renewable materials like cellulose is crucial. The films herein presented are generated by extruding a cellulose–ionic liquid solution through a distribution plate (DP) and slit nozzle into an aqueous coagulation bath, via an air gap. This study evaluates how different DPs and slit geometries affect the extrusion process and the film properties. Moreover, an automated continuous washing and drying system has been successfully implemented. The produced films are thin (13–17 μm), homogeneous, highly transparent (89–91%) and strong. The use of DPs resulted in very strong films (242 MPa, 10% elongation at break) but led to extrusion instabilities. Trials without any DP were stable, with films showcasing tensile strengths of 226 MPa and 9% elongation at break. Additionally, a numerical simulation was performed to understand the effects of the DPs and spinnerets' geometry on the dope flow.