N. Nygren-Sundell: Dope-dyeing of cellulosic fibres for sustainable textiles

Abstract: 

Textiles are an important part of our daily lives, but their production has a significant environmental impact globally. A potential solution to this could be to increase the use of recyclable, biodegradable, and bio-based fibres from renewable raw materials, such as man-made cellulosic fibres. The stage in the manufacturing process with the most environmental impact is dyeing. Normally, textile dyeing requires several harmful chemicals and large amounts of water, which contribute to water pollution.

A rise in consumer awareness of the drawbacks of fast fashion and its environmental impact, has begun to affect consumer behavior. In response to the growing need for bio-based and biodegradable fibers, our research has focused on developing an environmentally friendly dyeing strategy for textiles that minimizes energy consumption and water use.

The goal of this thesis was to develop an environmentally friendly dyeing technique for bio-based textiles. By combining dope-dyeing and Ioncell technology, we have achieved promising results. Dope-dyeing has previously been used for synthetic fibres manufactured in large quantities, such as black, dark blue, red, and brown. The Ioncell technology is an environmentally friendly manufacturing process for regenerated cellulose fibres using ionic liquid and dry-jet spinning. This technology offers flexibility with additives, which makes it possible to introduce dyes already during the fibre manufacturing process. This results in evenly distributed colors throughout the entire fibre matrix, improving color fastness against light, abrasion, and washing.

Our dyeing process eliminates the need for harmful chemicals, contributing to a cleaner production chain. Additionally, our research confirmed that textiles and their dyes can be recycled with the same technique. This innovative method can also be applied beyond the clothing industry, for example in the nonwoven sector. The dope-dyed fibres showed an excellent tensile strength of up to 50 cN/tex, surpassing most commercial cellulose-based fibers, and an elasticity between 10 and 13%.

Spin-dyeing of bio-based fibres can help reduce environmental impact within the textile industry and offer alternatives for more sustainable production methods in the future.

Keywords: Dope-dyeing, Vat dyes, pigments, man-made cellulosic fibres, nonwovens, cellulose

Opponent: Dr. Guillermo A. Reyes Torres, VTT Technical Research Centre of Finland

Supervisor: Professor Michael Hummel, Aalto University School of Chemical Engineering

Link to electronic thesis: Thesis available for public display 7 days prior to the defence at Aaltodoc.