Abstract:

Significance As an important regenerated cellulose fiber, Lyocell fiber has excellent properties and comprehensive preparation techniques, which has been attracted extensive attention. Owing to the green production process, Lyocell fiber has become the most promising regenerated cellulose fiber, which have extensively applied in various fields, such as textiles, clothing, household goods, and so on. The unique fibrillating properties of Lyocell fibers pose a challenge to the dyeing techniques. In the conventional Lyocell fiber dyeing process, in order to promote dyeing in an aqueous solution and improve the dyeing rate, plenty of water and salt auxiliaries have been used. However, these dyeing methods are facing environmental and energy challenges, including high water consumption, high energy consumption, the discharge of additives, and serious pollution of wastewater. Therefore, aiming at the current limitations, color construction of Lyocell fiber has been extensively investigated. In order to achieve color construction of Lyocell fiber with diverse colors, high fastness, eco-friendly processes, and promote the sustainable industrial development of resources and the environment, the latest progress in different technologies of color construction for Lyocell fiber and its products has been systematically summarized. +++Progress Environmental pollution associated with the conventional dyeing methods has been the research focus due to the use of salt reagents and wastewater. Therefore, attention has been attracted to the clean dyeing methods for the color construction of Lyocell fiber. This review paper focuses on the more environmentally friendly color construction methods of Lyocell fiber, including surface modification dyeing, dope dyeing, ultrasonic-assisted dyeing, and high-temperature vat dyeing. Based on the systematic analysis of the research status for Lyocell fiber color construction, the development and challenges of different dyeing methods were reviewed. Surface modification dyeing enables a more stable binding force between the fiber and dye, hence improving the color fastness and reducing the fiber fibrillation, but the dyeing process is limited by the complicated process. The technique of stock solution coloring omits the subsequent dyeing process of fiber, while the achievement of color types and color adjustment is difficult to solve. Ultrasonic-assisted dyeing contributed to the rapid transfer of dye from liquid to fiber, reducing energy consumption and the use of salt auxiliaries for which complicated process is inescapable. Complete chromatography, high color fastness, and short time are the characteristics of high-temperature vat dyeing. However, the energy dissipation is a key point to be overcome in the process of green development in the future. The utilization of natural dyes can reduce environmental pollution, and mordant dyeing can improve the dyeing effect, but the K/S value and color fastness is vital in the practical application process. +++Conclusion and Prospect Compared with the conventional dyeing methods, non-aqueous media dyeing technology not only helps reduce the wastewater discharge of the dyeing process, but also provides a new opportunity for the sustainable development of the dyeing industry in coping with water scarcity to promote green textile production and achieve sustainable development of the textile industry, promoting technological transformation and upgrading. Compared to the mentioned dyeing methods, appropriate non-water or less-water dyeing methods for cellulose fibers, which can effectively reduce water consumption and wastewater emission, show significant advantages of sustainable development. Related green dyeing technology has been widely investigated in cellulose fiber dyeing, which can apply to promote the green sustainable development of Lyocell fiber color construction, contributing to the establishment of a green ecological circular development system in the textile dyeing and finishing industry.

Key words: Lyocell fiber, color construction, surface modification dyeing, dope dyeing, ultrasonic-assisted dyeing, high-temperature vat dyeing, mordant dyeing, clean dyeing technique