A Study On The Processes Of Energy-saving Azo Disperse Dyes

C.I. Disperse Yellow211, C.I. Disperse Orange25and Disperse Red SE-2BL are three of the most widely used disperse dyes in the textile industry. The traditional production process were developed during1980s and1990s, which can not meet the requirements for cleaner production as well as government’s energy saving and emission reduction policy. This paper optimized the production process for these three products. With the addition of surfactant during the coupling step, it decreased the surface tension while increased the ratio of solid/liquid in the reactant, so that the water can be saved for the production. The results of both lab trial and plant pilot indicated:1) when the dispersing agent was added into the coupling components in the coupling process, it could increase the solid content of the coupling reactant to10%or more, thus could save at least1/2of water, compared to the traditional process,2) the particle size of the coupling products, i.e., dye crude, were smaller and easier to mill, thus the milling time could be reduced to1/3to1/2, so the powder needed for milling could be1/2less than the traditional process for milling the same particle size,3) since the particle sizes of the dye crude were smaller than the pore diameter of filter cloth used in the workshop, in order to recover the fine particles of dye crude, a membrane filtration process was needed. The main the composition of the filtrate1come out of the membrane filtration was water together with small amounts of dye crude and dispersing agents. So the filtrate1could be used as fresh water to prepare the coupling component. This kind of recycle could save even more water;4) the COD of the filtrate2after membrane filtration was between700～800, while the COD of waste water from the traditional process was over10000. In other words, the new process could obviously reduce the cost for treating waste water,5) the shade and color strength of the three dyes produced by new processes in PET fiber were almost the same as the ones produced by traditional processes when they were dyed for PET fiber.