Synthesis and process development of polyether polyol with high primary hydroxyl content using a new propoxylation catalyst

We have developed a novel class of propylene oxide-based polyether polyol (PPG) with up to 70% higher primary hydroxyl content, which is produced through a Lewis acid-mediated propoxylation reaction using a specific borane catalyst. Conventional PPGs produced via anionic ring-opening polymerization have secondary hydroxyls, resulting in poor reactivity in urethane formation. To overcome the poor reactivity, ethylene oxide (EO) is often added to the terminal hydroxyls of conventional PPGs. However, this modification decreases the humidity resistance of the resulting polymer. In contrast, our new PPG has enhanced primary hydroxyl content with little or no added EO, thereby achieving a good balance between reactivity and hydrophobicity. As a result, the new polyol has important advantages, such as enhanced durability, energy and resource conservation, and environmental load reduction for a broad area of polyurethane applications. In addition, we developed an innovative continuous process that uses tube reactors in combination with film evaporators for by-product removal. This review focuses on key technological innovations in process development and examples of the practical applications of the new PPG.