CHEMICAL ENGINEERING TRANSACTIONS VOL. 49, 2016 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Enrico Bardone, Marco Bravi, Taj alli Keshavarz Copyright © 2016, AIDIC Servizi S.r.l., I SBN 978-88-95608-40-2; I SSN 2283-9216 A Criteria for Evaluating the Microbiological Contamination of Acrylic Paints Vincenzo Piemonte a , Mauro Capocelli a , Francesco Tortora b ,Marina Prisciandaro* b a Faculty of Engineering, University Campus Bio-Medico of Rome, via Alvaro delPortillo 21, 00128 Rome, Italy b Department of Industrial and Information Engineering and of Economics, University of L’Aquila, viale Giovanni Gronchi 18, 67100 L’Aquila, Italy marina.prisciandaro@univaq.it The acrylic paint can be contaminated by bacteria (and rarely fungi), due to the presence of microbiological residuals on the container, that are responsible for the degradation of the paint chemical and physical characteristics. Hence, as stated by the EU regulation of May 2015, it is mandatory to provide an in-can preservation of the paint. When subject to different temperatures, the in-can product could evaporate and then condense under the cover of the can. Since biocides are not volatile substances, they are present in very small quantities in the cover phase setting the bacteria free to proliferate. This research group is working on the modelling of the microbiological evolution of in-can systems with the aim of predicting the contamination extent and of obtaining proper design procedures to guarantee the protection (of both the can and the cover phase). The thermofluid-dynamic model implemented on gPROMS software is validated through the comparison with literature experimental data. In this paper we present the criteria at the basis of the cited system modelling. More in detail, this work reports the thermodynamic (phase equilibria using NRTL model) and the kinetic fundamentals, the estimation of the kinetic parameters through a literature comparison and a case study (considering MIT biocide) considered for the model validation. Keywords: acrylic paints; microbiological contamination, gProms, model validation. 1. Introduction Biocides should provide both an in-can protection and the protection of the layer of paint once applied to the surface (Contant et al., 2010). The presence of microorganisms on the surface layer of the paint is undesirable since it may damage the paint considerably by causing even the discoloration. Moreover, the presence of microorganisms causes the increase of the porosity of the paint layer, a decrease in physical resistance and allows the moisture to penetrate the treated surface with, for example, consequent corruption issues in case of wood surface (Unger at al., 2013). The organic solvents used in the formulation of paints are increasingly replaced by water-based systems to meet the more stringent environmental regulations. As a matter of fact, when subject to different temperatures, the in-can product could evaporate and then condense again under the cover of the can. Since biocides are not volatile substances, they are present in very small quantities in the cover phase and the bacteria are therefore free to proliferate. The microorganism contamination may occur during the manufacturing stages of paint production and during the storage as packaged product (La Rosa et al., 2008). The use of effective broad-spectrum biocides, together with good manufacturing processes and plant hygiene, may ensure the long-term microbiologically trouble-free production to take place (Karsa and Ashworth, 2007). The right choice of a preservative system depends on the kind of microorganism, the physicochemical compatibility, the toxicity of the biocidal product and its final characteristics to be obtained. The biocides to be commercialized must satisfy the EU regulations for limiting the growth of microorganisms by means of the destruction of the cell membrane, the inhibition of metabolic reactions, the variation of intracellular pH and the accumulation of toxic anions. Among available molecules, typically used biocides as for in-can protection are: 1,2-Benzisothiazolin-3-one (BIT), 5-chloro-2- methyl-isothiazolin-3-one/2-methyl-isothiazolin-3-one (CMIT,MIT); Formaldehyde donors. Biocides used for DOI: 10.3303/CET1649002 Please cite this article as: Piemonte V., Capocelli M., Tortora F., Prisciandaro M., 2016, A criteria for evaluating the microbiological contamination of acrylic paints, Chemical Engineering Transactions, 49, 7-12 DOI: 10.3303/CET1649002 7