Partition and diffusion of volatile compounds from acrylic adhesives used for food packaging multilayers manufacturing

Partition and diffusion coefficients of volatile compounds in polymers have been broadly studied in the literature in order to provide the tools necessary to predict migration from the packaging materials to the food using the appropriate mathematical models. But often, food packaging materials are multilayer materials where several substrates are joint by adhesive layers. Little is known about the partition coefficients between adhesives and substrates used in these materials and about the diffusion coefficients in some of the materials commonly used such as paper or cardboard. All of these parameters will have a direct effect on the final migration of the compound. The objective of this work was to study the behaviour of the compounds found on the acrylic adhesives in 4 different real laminates. Partition coefficients between several types of acrylic adhesives and substrate materials (polyethylene, polypropylene, couche paper and kraft paper) were experimentally calculated. Moreover, diffusion coefficients of the compounds in these four materials were derived from experimental data. Finally, a migration test with Tenax was carried out. A wide variation of results for partition coefficients was found due to the difference on the chemical properties of the compounds studied. In fact, a relation between the coefficients and their Hildebrand solubility parameters was found. Moreover, the most relevant result found in the diffusion coefficient values was that the coefficients in paper were lower than in PE but higher than in PP. Migration results showed that only 4 out of 11 compounds were found in Tenax. Only 2,4,7,9-tetramethyldec-5-yne-4,7-diol belong to a high toxic class according to Cramer rules.