1. For direct dyes with high dyeing rate and good diffusion performance, the darkest color will be obtained at 60-70℃, but the dyeing rate will decrease above 90℃. When this kind of dye is dyed, in order to shorten the dyeing time, the dyeing temperature is 80-90℃. After dyeing for a period of time, the temperature of the dye liquor will gradually decrease, and the dye in the dye liquor will continue to dye the fiber to increase the dye uptake percentage.
2. For direct dyes with a high degree of aggregation, slow dyeing rate, and poor diffusion performance, increasing the temperature can speed up the dye diffusion, increase the dyeing rate, and promote the exhaustion of the dye in the dye solution, increasing the dyeing percentage. During the regular dyeing time, the temperature at which the highest percentage of dye uptake is obtained is called the highest dye uptake temperature.
According to the difference of the highest dyeing temperature, direct dyes are often divided into low-temperature dyes with the highest dyeing temperature below 70℃, medium-temperature dyes with the highest dyeing temperature of 70-80℃ and those with the highest dyeing temperature of 90-100℃. High temperature dyes. In production practice, cotton and viscose fiber knitted fabrics are usually dyed at around 95°C, while the dyeing temperature of silk knitted fabrics is relatively low, because too high temperature will damage the luster of the fiber, and the best dyeing temperature is 60-90°C. Appropriately lowering the dyeing temperature and extending the dyeing time are beneficial to production.