2,2,5,5-Tetramethyloxolane (TMO) replacing toluene as an azeotropic solvent for the synthesis of polyester resins

A diverse array of chemical substances, from small molecules to macromolecules such as polyester resins for coatings applications, are synthesized in large quantities by means of condensation and polycondensation reactions. Condensation reactions starting from acids and alcohols are commonly used in industrial procedures because they utilize inexpensive starting materials and water is produced as the only byproduct. To ensure efficient removal of the water, the reaction can be conducted under reduced pressure or assisted by azeotropic solvents. For the latter, toluene is often used. In this study we were interested in exploring whether 2,2,5,5-tetramethyloxolane (TMO) also known as tetramethyl-tetrahydrofuran can be used as a safer and benign alternative to toluene. Therefore, the azeotropic polycondensation of polyester resins was examined in the presence of toluene or TMO. Furthermore, the nature of the TMO-water azeotrope and the stability of TMO under the reaction conditions were explored and compared to toluene. Results obtained showed that TMO does indeed form an azeotropic mixture and can be used as a safer alternative to toluene to efficiently remove water in polycondensation processes.