Evaluation of dyeing and finishingcomponents in recycling and regeneration ofcoloured textiles prototypes

The ability to create secondary raw materials with low impurity content is importantfrom a fibre regeneration processing perspective. Cotton textiles contain colourantsand textile finish, which can be considered as impurities in a chemical recyclingprocess. Removal of such impurities in a decolourisation stage would enhance the fibredissolving capacity and stabilise and simplify the fibre regeneration process.Moreover, the removal of impurities from secondary raw materials is also importantfrom an environmental and health perspective. Chemical recycling has the potentialto deal with the risk of retaining or spreading hazardous substances further inre-circulated textile loops. Of specific concern are colourants or additives withcarcinogenic or endocrine disruptive attributes as well as bioaccumulative substancessuch as PFAS (per- and polyfluoroalkyl substances), which are commonly used intextiles for dirt and water repellency.This report describes an experimental evaluation of physical properties of decolourisedcotton regenerated into viscose fibres and an analysis of potentially hazardous textilefinish components throughout a decolourisation approach. The three main researchquestions in this report are:1. Can we obtain viscose fibres from a decolourised black cotton fabric withsimilar physical properties as commercial viscose fibres by using the re:newcelldecolourisation approach?2. Can the impact from a DMeDHEU(1) anti-wrinkle and a fatty acid softener finish onthe physical viscose fibre properties be eliminated using this decolourisation approach?3. Could chemical recycling be a potential solution for recirculation of textiles whichhave a risk of containing hazardous substances of for example PFAS dirt and waterrepellent type? The project has been performed within the Mistra Future Fashion research program byjoint work from re:newcell, MoRe research, Swerea IVF, Swedish School of Textile and RISE,and with support from the companies DyStar®, Lenzing AG, H&M, I:CO, Boob design,Wiges, New Wave Group, Filippa K and Kappahl. The part of the study that concerned thedirt and water repellent was performed in cooperation with the research project SUPFESfunded by the Swedish Research Council for Environment, Agricultural Sciences andSpatial Planning (FORMAS) under grant agreement No. 2012-2148.The study showed that viscose fibres can be produced from decolourised cotton usingthe re:newcell decolourisation approach. However, the desired physical fibre propertieswere not obtained. More optimisation in the decolourisation stage is needed to adapt thecotton substrate for the viscose process. A first indication of the softener to positively affect tenacity of the viscose fibre wasobserved. The anti-wrinkle treated fabric showed a tendency in higher reduced cloggingnumber, but no influence on the physical fibre properties was seen. While caution shouldbe taken in drawing conclusions from the few performed trials, it seems likely that theimpact from the tested types of anti-wrinkle agent and softener on the viscose processcould not be eliminated by the use of the decolourisation approach. This also raisesthe question of how persistent the softener is in a decolourisation process. The resultsfrom the analysis on dirt and water repellent substances (DWR/PFAS) throughout thedecolourisation process showed that one third remained in the pulp. This suggests thatthe DWR binds to the fibres in a way which the decolourisation process is not able toreverse.Taken together, these results are not sufficient to prove the hypothesis of whetherchemical recycling could be a potential solution for recirculation of textiles with risk forcontaining hazardous substances of this sort.The trials lead to the following conclusions: The used decolourisation approach haspotential to remove the type of reactive dye, wrinkle-free agent and softener tested inthis study. Adaption of the decolourisation process for the cotton substrate is neededin further trials. In the specific case of cotton flows with presence of dirt and waterrepellent finish we recommend designing of another decolourisation approach