Coal-derived, solid resins as economic raw materials for coatings

Solvent extraction of subbituminous coal at mild conditions (360°C) provides solid extracts that consist of numerous organic molecules that can be utilized in the synthesis of polymeric coatings. We describe the extraction process as well as the application of the resultant materials, which bear phenolic groups as the main reactive functionality, for the synthesis of polyurethane and epoxy coatings. The respective reactions of coal extract with isocyanates or epoxides were validated by ¹³C-NMR. By combining 50–67% coal extract with suitable, flexible co-reactants and co-resins, we formulated coatings with excellent wet adhesion to aluminum, flexibility, and corrosion protection with the same quality as reference coatings. The work is an advancement toward the goal of developing economic and resource-efficient routes from coal to polymers with attractive properties, where coal extracts can compete with petrochemically derived raw materials.