Progress in Supercritical Co2Dyeing

Supercritical fluids have special properties that could lead to substantial improvements when utilized as replacements for water in wet processing of textiles. These fluids have densities and solvating powers similar to liquid solvents combined with viscosity values and diffusion coefficients like those observed for gases. In particular, these properties make supercritical carbon dioxide (SC-CO ₂ ) one of the most beneficial and environmentally acceptable solvents used in manufacturing processes today. Therefore, it is anticipated that commercial textile processes using SC-CO ₂ will have many advantages when compared to conventional aqueous processes. Succesful commercialization of SC-CO ₂ processing will improve the economics of dyeing and other textile chemical processes by eliminating wastewater discharges, reducing energy consumption, eliminating drying, and reducing air emissions. As a result, the use of SC-CO ₂ is expected to make textile processing more economical and environmentally friendly. Research groups throughout the world are investigating SC-CO ₂ textile processing. Succesful pilot dyeing machines have been operated and even publicly exhibited within the past few years. Research focused to developing a commercial dyeing process for polyester yarn packages is in its sixth year within the College of Textiles at North Carolina State University. Process development has been accomplished using a single-package SC-CO ₂ dyeing machine located in the Model Manufacturing Facility of the College. This paper provides an overview of the status of the research and discusses the technical and economic factors important to the successful commercialization of an SC-CO ₂ polyester yarn package dyeing process.