Detergency in Liquid CO2

In this dissertation we study Detergency in liquid Carbon Dioxide. Detergency is the cleaning performance of additives, surfactants in particular, in washing fluids. Liquid CO2 is under consideration, for environmental and toxicological reasons, to replace perchloro-ethylene as the solvent in textile dry cleaning technology. Inherent problems of such a transition were confronted with the methodology of chemical engineering design. The Basic Cycle of Design (BCD) approach was used as a pathway for designing a detergent. The BCD also establishes the structural framework of the thesis, which can, therefore, be read as records from a successful product engineering project, in which an effective detergent has been designed for a new dry cleaning solvent. The Dynamic Detergency Model (DDM), which succeeds to explain the role of surfactants in the washing operation, is used as a rational starting point for the design of a detergent in liquid CO2. According to this model, such a surfactant must be: sparingly soluble in the solvent, surface-active and able to form micelles in the solution. The different experiments carried out (solubility, interfacial-tension and dye solubilisation measurements), show that a number of molecules of the homologous polyoxyethylene/alkane series, generally described by the shorthand formula CiEj did indeed behave as surfactants and can be then considered detergents for liquid CO2. In the technical evaluation of the detergents, at laboratory as well as at semi-pilot scale, high washing performances were obtained. They are, indeed, as good for dry cleaning textiles as the present perchloro-ethylene (Perc) technology