Preparation of aqueous polyurethane dispersions using aromatic diisocyanate

Abstract

Aqueous polyurethane dispersions were prepared by the reaction of hydroxyl-terminated polyethylene adipate), ethylene glycol, dimethylol propionic acid and aromaic diisocyante, 4,4′-diphenylmethane diisocyanate. The influence of molecular weight of oligoester and molar ratio between isocyanate and hydroxyl groups (NCO/OH) in the prepolymerization step were investigated. Molecular weight, particle size and particle size distribution were measured and compared. It was verified that the molecular weight increases with increasing in NCO/OH molar ratio. The results suggest that the hard segment content plays an important role in particle size and particle size distribution of the dispersions. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA,.