Polyorthoesters for Low-VOC Coatings

By Hisashi Isaka, Yoichi Yonehara

A series of new oligomeric polyorthoesters for low-VOC coatings was prepared by protecting OH groups with orthoester compounds to achieve both low viscosity and excellent compatibility with crosslinking agents. These new oligomeric polyorthoesters were synthesized through a co-condensation reaction among polyol, orthoester, and α- or β-glycol compounds under an acidic condition.

Here, the α-or β-glycol compounds were used as stoppers to prevent excessive polymerization. The poly-orthoesters can easily be hydrolyzed with atmospheric moisture, and the produced OH groups can react with appropriate crosslinking agents.

It is unique in this system that even the stoppers, α- or β-glycol compounds, can react with the crosslinking agents to achieve an extremely low VOC emission. The polyorthoesters cured with polyisocyanate compounds proved to be highly crosslinked polymers showing excellent mechanical properties, chemical resistance, etc.