Bio-based 1,5-Pentanediol as a Replacement for Petroleum-Derived 1,6-Hexanediol for Polyester Polyols, Coatings, and Adhesives

Amorphous and semi-crystalline polyester polyols based on a novel, low cost, bio-based 1,5-pentanediol (Bio-PDO) were synthesized and formulated into solvent-borne coatings and hot melt adhesives. Bio-PDO may provide a lower cost, more sustainable, and non-petroleum-based alternative to polyols based on 1,6-hexanediol (HDO). The polyester polyols were characterized for end group composition, monomer incorporation, and thermal transitions. Bio-PDO-based coatings exhibited performance, including hardness, flexibility, adhesion strength, and solvent resistance, similar to the coatings based on petroleum-derived HDO. Bio-PDO-based adhesives exhibited lower green strength (initial adhesion strength) and longer open time (workable time to bond substrates) than HDO-based adhesives. The effects of common bio-based impurities, including lactones and mono-alcohols (δ-valerolactone and tetrahydrofurfuryl alcohol as examples of impurities), on polyester polyols were investigated. Hydroxyl functionalities of polyols were controlled by the excess diols in monomer feeds and were not impacted largely by the δ-valerolactone levels. High-level tetrahydrofurfuryl alcohol terminated the polyester ends with unreactive functionality. Deleterious effects on polyol hydroxyl functionality are not expected at the low impurity levels (<2 wt %) found in leading bio-PDO processes.