High Tg amorphous polyester polyols have been widely used in polyurethane hot melt adhesive applications due to their ability to improve green strength, adhesion to various substrates, as well as heat and chemical resistance of the bonded structures. However, conventional high Tg amorphous polyester polyols usually possess high melt viscosity, leading to higher viscosity of the formulated adhesives and causing quality inconsistencies in applications. In addition, conventional high Tg amorphous polyester polyols demonstrate poor compatibility with common key components in polyurethane hot melt adhesive formulations, such as polyether polyols and hydrocarbon-based tackifiers. This paper highlights recent developments of high Tg and low viscosity polyester polyols based on 2,2,4,4-Tetramethyl-1,3-cyclobutanediol (TMCD). By incorporating TMCD in the polymer backbone, a similar glass transition temperature can be achieved of a workhorse product but at 6 times lower viscosity, resulting in improved application consistency. Additionally, the TMCD-based polyester polyols demonstrate outstanding hydrolytic stability at elevated temperatures and enhanced compatibility with the key components of polyurethane hot melts. Most interestingly, adhesives containing the TMCD-based polyester polyols exhibit greater adhesion strength to low surface energy substrates. All these performance attributes significantly improve quality consistency, simplify application, and reduce cost-in-use for converters, while expanding design space for formulators.
Co-author: Rui Xie