Disperse dye

Disperse dyes are a class of nonionic dyes which have a very low water solubility and which are present in a highly dispersed state in the form of fine particles in water by means of a dispersing agent. It is mainly used for dyeing polyester fibers. The chemical structure of most disperse dyes belongs to the monoazo type, which accounts for about 80% of the disperse dyes, followed by about 15% for the indole type and about 5% for other structural types. It is generally believed that the dyeing mechanism of disperse dyes in water is: due to the action of the dispersant, at the dyeing temperature, part of the dye is dissolved in the dyebath to become a dye molecule, and then adsorbed on the surface of the fiber in the form of molecules, at the same time The amorphous region in the ester fiber is expanded at the dyeing temperature to form a cavity sufficient to accommodate the dye molecules, so that the dye molecules are easily diffused in the fiber, and at the end of the dyeing, the previously expanded holes shrink as the temperature decreases. The dye molecules are encapsulated within the fibers such that the dye molecules are ultimately fixed in the fibers in the form of single molecules or low molecular aggregates. Some foreign scholars believe that the crystal form of disperse dyes (ie, crystal form) has an effect on its dyeing properties, but later research results negated this claim. However, the crystal form of the disperse dye is different, and its lattice energy is also different, so the crystal form of the disperse dye has an influence on its commercial processing. Disperse dyes can be divided into five series: (1) E-type disperse dyes, with good leveling performance, suitable for dip dyeing process, and some can be used for thermal transfer printing process. (2) SE type disperse dyes, which have general leveling properties and good sublimation color fastness, can be used for polyester fiber dyeing process and hot melt dyeing process. (3) S-type disperse dyes with high sublimation color fastness, mainly used for hot melt dyeing of polyester blended fabrics. (4) P-type disperse dyes, suitable for anti-discharge printing of polyester fiber and cellulose fiber blended fabrics. (5) RD type disperse dyes, which can be used for rapid dyeing of polyester fibers. From the molecular structure of the disperse dye, there are mainly types such as azo, anthracene, nitrodiphenylamine and heterocyclic. Since the molecule does not contain a water-soluble gene, the disperse dye dissolves extremely little in water. There are two commonly used dyeing methods for disperse dyes, namely high temperature and high pressure method and hot melt method. The so-called high temperature and high pressure actually have a temperature of only 130 ° C and a pressure of only 0.2 MPa (gauge pressure). The reason for this is that the dyeing of other dyes is usually carried out under normal pressure, and the dyeing temperature generally does not exceed 100 °C. The dyeing by hot melt method is not carried out in water, but the dyeing solution of the dye is first padded on the surface of the fiber, and after drying, the fiber is sent to a drying room at 180-220 ° C for 30 s, in which the dye is sublimed. And the fiber is colored. According to such a dyeing process, the disperse dyes can be classified into three types: high temperature type, medium temperature type, and low temperature type. Disperse dyes belonging to the high temperature type are among the varieties having the largest molecular weight and the best sublimation fastness.