dl-Limonene as an Alternative Sustainable Solvent to Xylenes for the Industrial Preparation of Release Formulations

Many industrial processes use aromatic hydrocarbons as solvents, including benzene, toluene, ethylbenzene, and xylene (BTEX). However, their use is discouraged due to their toxicological profile. Research is ongoing to find alternative more sustainable solvents. This work explores the adoption of dl-limonene as an alternative to BTEX for the industrial preparation of release formulations containing carnauba wax to be employed in the peelable foils industry. A preliminary chemical-physical characterization of carnauba wax was carried out using spectroscopic (ATR-FTIR, NMR) and thermal analyses (DSC). Based on the chemical composition found for the carnauba wax used in the present study, different solvent mixtures and different concentrations of carnauba wax were tested to obtain a clear and stable solution. The most promising formulations were subjected to a coating test on a solid substrate (polyethylene terephthalate, PET) on a laboratory scale, followed by a peeling test to assess the resulting peeling strength. The dl-limonene/ethyl acetate mixture in the 9 : 1 ratio has been identified as the most suitable to completely solubilize carnauba wax (0.38 wt/vol %) and obtain an adequate release performance. The results of these experiments were then used to set up and successfully perform an industrial-scale coating test.