This work describes the hydroxyethylation of coal extract with ethylene oxide (oxirane) and the application of the extract as polyols in a polyurethane coating. Possible end uses include primers for corrosion protection, which can tolerate the extract's brown color. The extract was obtained by solvent extraction of subbituminous coal. Aromatic hydroxyl groups (phenolic groups), the extract's main functionality, are converted to aliphatic hydroxyl groups. We discuss the effect of different hydroxyethylation conditions on the turnover of phenolic groups and on the formation of polyether chains as a byproduct and analyze reaction products by NMR, mass spectrometry, and Fourier transform infrared spectroscopy (FTIR). The coal extraction process and the application of extracts as polyols in polyurethane coatings have previously been described, motivated by the goal to identify nonfuel uses for the abundant, economic coal. These previously described coatings had shortcomings in the low thermal stability of carbamate (urethane) linkages formed by phenolic groups, as well as a low cross-linking density when cured at room temperature due to the steric hindrance of phenolic groups in the coal extract. The present work overcomes these shortcomings by modifying the coal extract to provide aliphatic hydroxyl groups. This modified coal extract was then utilized as the polyol component in an ambient-cure, two-component polyurethane coating, which had comparable adhesion, flexibility, and chemical resistance as a reference coating based on commercial resins.

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