Overview of Practical and Theoretical Aspects of Mineral Oil Contaminants in Mill Process and Paperboards

Abstract

The paperboard industry is committed to consumer protection in food packaging and has assigned top priority to the issue of mineral oil hydrocarbons (MOH) as early as spring 2010. In this work, we have developed practical methods, using gas chromatography with a flame ionization detector (GC-FID) laboratory equipment, to characterize the level of mineral oil saturated hydrocarbons (MOSH) and aromatic hydrocarbons (MOAH) in European and North American newspapers, paperboards, and inks. As part of our validation protocol, several samples were analyzed by an external laboratory (ISEGA, Aschaffenburg, Germany) using Biedermann’s protocol and an average deviation of 6% for the MOSH and 17% for the MOAH was observed between ISEGA and our method. Using the reference Tenax migration method (EN, 14338), the hexane or heptane vapour transmission rate (HVTR) method was developed to measure the barrier efficiency within one day, showing a very good correlation; R² = 0.80 to 0.92.

Much higher MOH concentrations in newspaper printed areas infer that printing inks constituents are the most likely source of MOSH/MOAH in recycled paperboard. When processing such raw material, the drying section is one of the paperboard making process steps that significantly reduces the MOSH and MOAH level. Although low or free mineral oil printing inks would be preferable, the use of functional barriers can significantly reduce the migration of MOSH/MOAH, whenever necessary. Mineral oil migration barrier efficiencies of about 90% were obtained using polymeric functional barriers applied at the mill with conventional coating equipment. Finally, a first attempt was made to theoretically model the migration of mineral oil through model polyacrylate functional barriers. The correlation between calculated (theoretical) and experimental hexane permeabilities seems reasonable and a predictive discrimination between good and bad barrier polymers appears possible for acrylate copolymers (R²=0.72) within foreseeable limitations with respect to chemical composition.