Washing of pollution-preventing lithographic inks from a roller drum

The share of lithography is sizable in the printing industry. Conventional lithographic inks usually contain a volatile organic compound (VOC) as a solvent. Ink rollers and plates are cleaned in place with a solvent, usually a VOC. Emissions of VOCs become a major cause for air pollution. A newly developed water-washable ink system eliminates the use of petroleum-based solvents and avoids emissions of VOCs during printing and cleaning of presses. The presses are cleaned by washing with water at a slightly elevated pH. Washing kinetics of this ecofriendly ink on a prototype roller drum are discussed. An empirical correlation between the mass-transfer coefficient and the process variables is sought based on experimental data on washing of the prototype roller drum. This correlation may be useful in deciding the optimum resin concentration in ink, the pH of the wash solution, and the speed of roller drum during cleaning of the presses. The mass-transfer coefficients obtained on the roller drum are very large as compared to those on a revolving watch glass in the low-shear experiments reported earlier (Bhaskarwar, A. N.; Cussler, E. L. Chem. Eng. Sci. 1997, 52 (19), 3227-3231; Nair, S.; Bhaskarwar, A. N. Chem. Eng. Sci. 2000, 55 (10), 1921-1923).