Biodegradation of acrylic paints: modelling of biocide effect on biomass growth at different temperatures

Acrylic paint, notwithstanding the attention paid during the production process, couldbe contaminated by bacteria. This is a consequence of microbiological residuals on the can, resulting in the alterationof paint characteristics. It is therefore necessary to provide an in-canpreservation of the paint by using a biocide.In this paper, the evolution of an in-can system, using a thermo-fluid dynamic model is presented; as a biocide, 2-methyl-4-isothiazolin-3-one, commercially known as MIT,was considered. The model was implemented on gPROMSsoftware and it was possible to determine the inhibitory concentration of the biocideinorder to guarantee both the protection of the can and the protection of thecover phase. To develop the model, kinetic parameters have been found by fitting available literature experimental data. As far as the thermodynamical parameters, theequilibrium between liquid and vapor phases was described bythe NRTLmodel (ASPEN Plus). The model has been validated through a comparison with experimental literature results using MIT alone and a mixture of biocides (MIT/BIT). The main results are that,at the maximum allowable concentration (100 ppm as imposed by law), the MIT biocide is able to protectthe paint for long periods, even when the temperature varies cyclically from 10 to 40°C.