A method for the preparation of dye powders as colorless diluents

摘要

PURPOSE:To produce a dry dye of good quality with good thermal efficiency, by a method wherein a dye stock solution is dried under specified conditions by using a spray dryer. CONSTITUTION:Hot air 2 supplied through a duct 2-a is introduced as a high-speed jet stream into a drying chamber 4 by means of a venturi tube 2-b (an accelerating mechanism). A dye stock solution 1 (a dispersion or a solution of a dye) is sprayed on the hot air from a nearly central part over the drying chamber by a nozzle type atomizer to atomize the stock solution. whereby water in liquid droplets is instantaneously evaporated to dry the dye. The dye is then withdrawn as a product 3 from an effluent duct 3-a. In the above process, the stock solution is dried at an inlet temp. (the temp in the neighborhood of the duct 2-a) of 110-260 deg.C, at an outlet temp (the temp. in the neighborhood of the duct 3-a) of 60-80 deg.C and at a hot air rate of 5-80m/sec just under the atomizer (or in the neighborhood of the atomizer). By providing a cold air-blowing port 5 at the top of the drying chamber, the stock solution can be dried more efficiently while inhibiting the thermal deterioration of the dye.