Advantages and Disadvantages of Reactive Dyes
By: Alfa Chemistry
Since the reactive dye is composed of parent dye, linking group and active group, it can form a strong covalent bond with the fiber during dyeing, and so it has a series of characteristics unmatched by other cellulose fiber dyes. These characteristics make reactive dyes the main dyes used to dye cellulose fibers. The advantages of reactive dyes are manifested in the following four aspects:
(1) Reactive dyes are one of the best alternatives to banned dyes and other types of cellulose dyes such as sulphur dyes, azoic dyes and vat dyes.
(2) Dyed materials having excellent properties, particularly good wet fastness, can be obtained by dyeing with reactive dyes through an economical and simple dyeing process.
(3) The reactive dyes have wide chromatogram, bright color, excellent performance and strong applicability, and their properties can satisfy the requirements of the market for fibers and fabrics.
(4) Reactive dyes are suitable for dyeing of new type of cellulose fiber products such as Lyocell fibers.
Disadvantages of Reactive Dyes
The main technical problems of reactive dyes are as follows:
(1) The utilization rate is not high enough (generally 60%~70%). The dyeing process produces a large amount of colored sewage, and its COD value is generally between 0.8 and 30,000 ppm, and the COD value of concentrated wastewater is more than 50,000 ppm.
(2) In order to suppress the charge on the surface of the fiber, a large amount of electrolyte is consumed when using the reactive dye, which not only increases the labor intensity, but also raises the concentration of chloride ions in the wastewater to more than 100,000 ppm, thereby greatly increasing the difficulty level of the treatment of dyeing wastewater.
(3) Some reactive dyes cannot meet the requirements of the market, such as their light fastness to wetness, wet rubbing fastness, and the light fastness of azo red dyes and azo blue dyes in light colors.
(4) There are few dark varieties of reactive dyes that can replace sulfur dyes (https://www.alfa-
At present, the main solution to the technical problems of reactive dyes is to increase their sorption rate and fixation rate. The most effective method is to introduce two heterologous or homologous active groups into the reactive dye molecules, for example, introducing two heterologous active groups - Chlorine Triazinyl and vinylsulfone groups. The novel reactive dyes composed of these two heterogeneous reactive groups and a suitable parent dye and a linking group have properties such as low acid hydrolysis rate, high acid hydrolysis bond breaking stability, excellent washability, good fastness and small difference between sorption rate and fixation rate. And the new reactive dyes also have new properties resulting from the interaction of the two different reactive groups, such as better acidic hydrolysis resistance, higher fixation rate, wider dyeing temperature range, better dyeing reproducibility and they are suitable for medium temperature dyeing, low temperature dyeing and high RFT dyeing, etc. Therefore, the production of such reactive dyes has accounted for two-thirds of all reactive dyes for dyeing, and reactive dyes have become the main dyes for pad dyeing and dip dyeing of cotton fabric.