(105a) New Pollution - Preventing Anionic Lithographic Printing Inks: Washing Kinetics Studies Under Low and High Shear Conditions

Printing presses use aliphatic and aromatic solvents for cleaning various surfaces which are coated with the ink. The conventional printing inks also contain volatile solvents. During printing and cleaning operations, volatile organic compounds (VOCs) present in the inks and cleaning solvents are lost to the atmosphere by evaporation and these losses are alarmingly high. A new type of ink based on castor oil, which completely eliminates emissions of VOCs, has been developed. Synthesis of resins and the kinetics of washing of the ink, similar to the pollution-preventing ink announced by Deluxe Ink Incorporation (Pennaz, 1994b), with water at a slightly elevated pH are studied. A correlation between the mass-transfer coefficient characterizing the washing of ink and the experimental process variables (Bhaskarwar and Cussler, 1997) were examined earlier by Maji and Bhaskarwar (2003). A new empirical correlation between the mass-transfer coefficient and the variables is sought based on the experimental data on washing of ink under low and high shear conditions (Watch glass and Prototype Roller Drum experiments respectively). These correlations may be useful in deciding the optimum resin concentration in ink, the pH of wash solution, and the speed of roller drum during cleaning of 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 and Cussler, 1997; Nair and Bhaskarwar, 2000; Maji and Bhaskarwar, 2003). The experimental data moderately support the theoretical expression for washing of inks under excess-base conditions. The washing of these inks under excess-resin conditions, however, appeared to be only slightly dependent on the theoretically anticipated combination of process variables and instead seemed to have an appreciable contribution of hydrodynamic factors (Sarkar, 2004).

Keywords: Lithographic inks, VOC emissions, Pollution prevention, Washing kinetics, Mass transfer coefficient, Watch glass, Roller drum, Printing, Empirical correlation.

+ Research Associate, Department of Chemical Engineering, Indian Institute of Technology, Delhi, India.

e-mail : chandrakantsarkar@gmail.com

* Petrotech Chair Professor. Author to whom all correspondence should be addressed.

e-mail: ashoknb@chemical.iitd.ernet.in, anbhaskarwar@gmail.com

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