Abstract: When dyeing cotton fibers with reactive dyes in the traditional water bath system, a large number of neutral inorganic salts need to be added to address the charge repulsion between the dye anions and the fibers in order to improve the reactive dye utilization. At the same time, a large amount of alkali must be used to ensure that the reactive dye can fully covalently bond with the fibers. However, the large amount of inorganic salts will lead to super high salt content in the dyeing wastewater, which increases the difficulty and cost of post-processing. At the same time, inorganic salt has brought a great threat to the ecological environment and water resources. Therefore, the low-salt and salt-free dyeing technology has become a hot spot in the current printing and dyeing industry. In order to realize the clean dyeing process of cellulose fibers with water saving, energy saving, high efficiency and ecological protection, researchers have done a lot of work. 
In this paper, the problems and limitations in the development of low-salt and salt-free dyeing technology were summarized from the development of new dye molecular structure (original structure modification and cationic reactive dyes), multi-functional substitute salts development and application, low-salt dyeing additives, cellulose modification, and non-aqueous medium dyeing technology. For the traditional water bath system, the modification of the reactive group, water-soluble group or chromophore on the structure of the existing reactive dyes, or the redevelopment of cationic reactive dyes, all have the problems of high cost, few categories, and incomplete chromatography. It is very low to realize salt-free and low-salt dyeing process as well as water saving and emission reduction by using other organic substitute salt, or crosslinking agent. Although widely studied cationic modification technology of cotton fabrics can reduce the dosage of inorganic salts, cationic modification and dyeing cannot be carried out in the same bath. This process requires pre-treatment of cotton fabrics, which has the problem of long process, high production cost, and difficulty in controlling the dyeing evenness. In addition, small bath ratio, electrochemical dyeing, and suspension dyeing have high requirements for dyes and poor universality. As for the new non-aqueous medium dyeing technology, the medium used in the early reported organic solvent dyeing technology is highly toxic and difficult to recover. While, the most reported supercritical CO2 dyeing cannot make cotton fibers swell, resulting in low dye adsorption rate and dyeing depth. In addition, the dyeing process needs to be completed under ultra-high pressure, which has the problems of low operational safety and high equipment cost. 
At present, the non-aqueous medium dyeing technology using high boiling point D5 as the medium has achieved remarkable results. But this technology also needs special dyeing equipment (dyeing, recycling, etc.) in the early stage, and the investment cost is high. Therefore, it is imperative to develop an economical, universal, water-saving, and emission-reducing non-aqueous medium dyeing technology in the future.

Key words: low-salt/salt-free dyeing, non-aqueous medium dyeing, reactive dye, cellulose fiber

摘要： 高含盐量的废水存在处理难度大、破坏生态环境等问题，严重阻碍了整个染整行业的可持续发展。因此，低盐无盐染色技术成为印染行业关注的热点。首先，介绍了纤维素纤维活性染料染色时无机盐的作用原理；接着，基于传统水浴染色技术，探讨了通过多功能代用盐、添加助剂、染料或者纤维素纤维结构改性等方式来实现低盐无盐染色技术的发展现况，并与非水介质染色技术进行对比，系统地阐述了活性染料低盐无盐染色技术的优劣势。分析结果可为开发经济适用、普适性高的活性染料无盐、节水减排质染色技术提供参考。

关键词: 低盐无盐染色, 非水介质染色, 活性染料, 纤维素纤维