Development of Renewable Polyester Resins for Coil Coatings Based on 2,5-Furandicarboxylic Acid

In this work, the development of FDCA-based polyester resins for coil coatings in industrial environment is presented. The goal of our research was to prepare industrial coatings made from renewable materials with the same performance as the standard coating. Resins with 1%–41% of FDCA on polymer were synthesized and then used in a formulation for primer. Resins were characterized by the determination of non-volatile matter, acid value, hydroxyl value, glass transition temperature, and measurement of viscosity, color and molecular weight. Coatings were characterized by the determination of viscosity, density, non-volatile matter, adhesion, T-test, MEK test, reverse impact, and pencil hardness, as well as the measurement of gloss. FTIR measurements confirmed successful incorporation of FDCA into the polymer. The results showed that resins with up to 31% of FDCA on polymer can be used to prepare coil coating where the properties of resins comply with the requirements and are comparable to the properties of standard resin. Resins had non-volatile matter between 59.0 and 60.1%, an acid value up to 4.6 mg KOH/g, a hydroxyl value of 22.0–24.9 mg KOH/g and viscosity at 23 °C between 6100 and 7500 mPa.s. Nevertheless, with the increase in FDCA in the formulation, discoloration of the resin occurred and incompatibility with the solvents was observed, while up to 10 °C lower glass transition temperatures and up to 28% lower molecular weights of the resins were determined. For coatings prepared from FDCA-based resins, the properties improved or were comparable to the properties of coating prepared from standard resin. Adhesion improved with higher content of FDCA in the resin from 2 Gt to 0 Gt, while all coatings had gloss at 60° of 39%–41%, a reverse impact of 10 J and a pencil hardness of H/2H. T-bend test results varied between 2 T and 0.5 T and the results of the MEK test showed resistance > 100 DR.