Supercritical cleaning of rollers for printing and packaging industry

Printing or film coupling processes use engraved rollers whose surface is formed by microscopic cells that carry inks or adhesives on the film. During their use, cells are progressively filled up of residual dry ink and/or adhesive that reduce their efficiency. Cells cleaning is very complex, due to their microscopic dimensions. A new technique based on the use of supercritical mixtures (carbon dioxide and organic solvents) to clean engraved rollers was developed. To study the feasibility of this process, various combinations liquid solvent-supercritical CO2 and the effect of some operating parameters was investigated, as operating pressure, temperature and residence time. Due to supercritical fluid mixture characteristics as, near zero surface tension and high diffusivity, a fast and complete removal of the dried residue from the microscopic cells was obtained. An almost complete cleaning was obtained in 40 and 60 min operating with a supercritical solution of carbon dioxide plus 80% w/w of N-methyl pyrrolidone at 150 bar and 40 degrees C for poly-urethane adhesive and polychlorovinyl resin red ink, respectively. (c) 2006 Elsevier B.V. All rights reserved.