A sustainable approach to produce light-colored rosin and rosin esters during processing using natural antioxidants

abstract

Rosin is a biobased product from pine trees used as raw material in several industries. However, rosin is prone to oxidation during thermal treatments, causing material degradation and particularly darkening. Synthetic anti- oxidants are used to produce light-colored rosin or rosin esters. Nevertheless, concerns about their use have prompted searches for natural alternatives. This study aims to replace synthetic antioxidants with natural al- ternatives for rosin processing. A preliminary screening of eight natural antioxidants allowed to show that by using α-tocopherol or thymol, rosin samples with Garnder color very similar to those obtained using the synthetic antioxidant Lowinox TBM-6 can be obtained. Further analysis was carried out by combining them with iodine, with inert atmosphere or both. Results showed that similar values of Gardner color, acid number, and softening point can be obtained using Lowinox TBM-6 and natural antioxidants and, when combining α-tocopherol or thymol with inert atmosphere and iodine, the resulting rosins or rosin esters have better Gardner color than by using Lowinox TBM-6. Moreover, gas chromatography coupled with mass spectrometry (GC-MS) and Fourier transform infrared coupled with attenuated total reflection spectroscopy (FTIR-ATR) analysis showed that rosins and rosin esters with similar chemical compositions can be obtained using synthetic and natural antioxidants confirming the enormous potential of the natural alternatives for the oxidative stability of rosin and rosin esters. Finally, the detailed GC-MS analysis of rosin samples enables understanding the essential role of iodine combined with the antioxidants to prevent rosin darkening.

authors

N. Seixas, J. Serrano, S. Pinto, B. Araújo, B. Viola, C. Vilela, S.A.O. Santos, C.S.R. Freire, A.J.D. Silvestre

Groups

G4 - Renewable Materials and Circular Economy

Projects

Inovação na Fileira da Resina Natural para Reforço da Bioeconomia Nacional (RN21)

Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)

Nano-argilas para remoção/captura de fosfatos (P) e sua reutilização como fertilizante (NATURAL)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

This research was developed within the scope of the Integrated Project RN21 - Inovaç˜ao na Fileira da Resina Natural para Reforço da Bioeconomia Nacional, is co-financed by the Environmental Fund through Component 12 – Promotion of the Sustainable Bioeconomy (Investment TC-C12-i01 – Sustainable Bioeconomy No. 02/C12- i01/ 202), of the European funds allocated to Portugal by the Recovery and Resilience Plan (PRR), within the scope of the Recovery and Resilience Mechanism (MRR) of the European Union (EU), framed in the Next Generation EU, for the period 2021–2026. The Project CICECO-Instituto de Materials de Aveiro, UID/50011/2025 (DOI 10.54499/UID/50011/ 2025) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020), financed by national funds through FCT/MCTES (PIDDAC) is also acknowledged. Acknowledgements are also due to FCT/MCTES for the research contract under Scientific Employment Stimulus to S.A.O. Santos (2021.03348. CEECIND).