Intensification of wet textile processing by ultrasound application

The application of ultrasounds in dyeing and washing industrial treatments is an important research theme because, as can be seen from a literature survey, this technique seems to be able to reduce the environmental impact and costs of these fundamental processes. In the frame of the Regional Project INTEXUSA concerning the intensification of dyeing and washing processes, a preliminary study was carried out with the aim of evaluating the dyeing kinetics improvement by ultrasound (US) application at different operative condition from a point of view of the process parameters. The tests were carried out in a pilot apparatus in which a significant quantity of fabric can stand (or move) over the ultrasonic transducer with variable power and frequency. The US multi frequency transducer was rectangular, flat with 500 W power and dimensions 400 x 150 x 80 m3; the wool fabric was tested at different exposure time and dyebath ratio of 1:70. Also the influence of the distance of the fabric from the US transducer was examined. During the dyeing experiments, for each trial, the dye-bath exhaustion curves has been determined by using an UV-Vis spectrophotometer and by detecting the other parameters (pH, temperature) with an online diagnostic equipment. For every dyeing isotherm, the apparent activation energy of the dyeing kinetics was calculated. In addition color fastness, artificial light and rubbing tests, which are related to the fabric quality, were measured. The research allowed the definition of the parameters which play have the most relevant role in the dyeing “ultrasonic” process.