Dry-jet wet spinning using 1,5-diazabicyclo[4.3.0]non-5-enium acetate as a powerful cellulose solvent is a promising technique for the production of high-strength man-made cellulose fibers not only from wood pulps but also from cellulose-based waste textiles. The regenerated cellulose fibers from waste cotton revealed very high tenacities up to 900 MPa exceeding the tenacity of the strongest virgin cotton fibers and that of commercial man-made cellulosic fibers1. The favorable mechanical properties of the spun fibers from recycled cotton waste can be explained by a small fraction of low molecular weight cellulose and the high total orientation of the cellulose chains along the molecular axis.
However, textiles on the market represent almost exclusively multi-component garments with cotton polyester blends being the most prominent mixture. This poses severe challenges onto their recycling due to their inherent heterogeneity.
Quite recently, we have demonstrated that it is possible to dissolve the cotton component selectively, while the residual and purified polyester experiences almost no degradation. After filtration, the cellulose solution is subjected to dry-jet wet spinning to obtain a Lyocell-type man-made cellulose fiber. At the same time, the recovered polyester can be fed to a melt spinning plant where it can be spun to new textile fibers either as a pure component or in a mixture with fresh polyester.
Moreover, systematic studies on the recycling of white fine paper and cardboard were carried out to elucidate their potential as raw material for the production of high-quality textile fibers. The raw material was refined gradually to identify the minimum refining needed to turn waste material into feedstock for man-made cellulosic fibers3. Finally, the spun filaments were cut to staple fibers and converted to yarns and knitted prototype fabrics to demonstrate the potential of lignin as a dye substituent.
1Asaadi, S.; Hummel, M.; Hellsten, S.; Haerkaesalmi, T.; Ma, Y.; Michud, A.; Sixta, H. ChemSusChem (2016), 9, 3250-3258.
2Haslinger, S.; Hummel, M.; Sixta, H. CELL-42, 253rd American Chemical Society National Meeting&Exposition, San Francisco, CA, April 2-6, (2017).
3Ma, Y., Hummel, M., Määtänen, M., Särkilahti, A., Harlin, A., Sixta,H. Upcycling of waste paper and cardboard to textiles. Green Chem., 2016, 18, 858-866.