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. The establishment of a Lewis acid-mediated selective propoxylation reaction using a specific borane catalyst enabled the synthesis of a novel class of PPG with an increased primary hydroxyl content of up to 70%. In addition, we developed a high yielding continuous process for producing the new PPG with a low amount of by-products by using tube reactors combined with film evaporators for by-product removal. Our new PPG achieves an excellent balance between reactivity and humidity resistance. As a result, it has important advantages for a broad area of polyurethane applications.