Towards a Closed Loop Economy in Textile Industry: Separation, Dyeing and Re-Spinning of Cellulose Rich Textile Waste

Abstract

This thesis targeted to improve the waste management in textile industry in terms of material identification, waste valorization and implementation of sustainable alternatives to commercial dyes and finishing agents. A solid-state NMR method was developed to quantify the amount of cellulose in cotton polyester blends, employing a relationship between distinct peak ratios and the cellulose concentration. Furthermore, the Ioncell technology allowed to utilize both, cotton polyester blends and dyed cellulose waste, to spin new, textile grade cellulose fibers via an ionic liquid solvent system. The produced filaments displayed tensile properties superior to commercial Viscose and Tencel with titers down to the microfiber range (<1 dtex). It was also shown that the ionic liquid, 1,5-diazabicyclo[4.3.0]non-5-ene acetate, enabled to dissolve cellulose, while leaving behind a polyester residue, which could be recovered for conventional recycling procedures. Similarly, dyed pre- and post-consumer cotton waste was converted to pristine, colored staple fibers, which were used to manufacture a scarf and a baby jacket. In many cases, the original color of the waste fabrics translated to the new textile products, although a certain amount of leaching could be observed during the spinning process. This behavior was dependent on the nature of the dyes and was hence more pronounced for reactive dyes such as Remazoles than for vat dyes. Eventually, gold and silver nanoparticles were assessed to replace potentially polluting dyes and finishing agents. Via a hydrothermal in-situ synthesis approach, spherical nanoparticles were prepared on bleached prehydrolyzed kraft pulp, which was subsequently dry-jet wet spun to colored, UV protective man-made cellulose fibers. As a result of the incorporation technique, the fibers exhibited a better wash fastness than substrates coated via immersion or in-situ reduction only. This demonstrated that the Ioncell process offers versatile opportunities for waste reduction as it tolerates different raw materials and impurities such as synthetic fibers and colorants.