Spin-dyeing of cellulose fibres with vat dyes using the Ioncell process

Estimated 20 % of global clean water pollution is attributed to textile production. Dyeing and finishing processes use an extensive amount of water and chemicals, and most of the effluents and wastewater is released into the environment. In this study, we explore spin-dyeing of man-made cellulosic fibres (MMCFs) with vat dyes using the Ioncell process, circumventing the ubiquitous use of fresh water and potentially reducing effluents streams to a great extent. Spin-dyeing is an established process for synthetic polymers but is not common for MMCFs. Regenerated cellulose fibres were produced through dissolution of dissolving pulp in the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-ene acetate. The produced fibres were processed into yarn and a jersey fabric was knitted. Mechanical and colour fastness properties were tested. The fibres properties were also assessed through SEM, birefringence, and crystallinity measurements. Fibres with excellent mechanical properties (tenacity higher than 50 cN/tex) and colour fastness were produced, with most samples receiving the highest or next highest performance grade. The spun-dyed fibres also hold great potential to be recycled themselves without colour change or loss in colour intensity. Textiles with colours produced in large quantities such as black or navy blue could be the first market entry point.