Making water dispersible/reducible blocked-isocyanates facilitates incorporation of blocked-isocyanates into an aqueous dispersion of co-reactant. Anionically modified methyl ethyl ketoxime (MEKO), ε-caprolactam (CL) and 3,5-dimethylpyrazole (DMP) blocked aromatic diisocyanates (toluene 2,4-diisocyanate, TDI and 4,4′-diphenylmethane diisocyanate, MDI) dispersible isocyanate adducts were prepared by introducing ionic pendant groups and characterized by FT-IR, gel permeation chromatography (GPC), differential scanning calorimeter (DSC) and thermo-gravimetric analyses (TGA) techniques. It was found that molecular weights of MDI-based polyisocyanates were higher. Thermal studies showed that the de-blocking temperature of the isocyanate adducts decreases in the order: ε-caprolactam > methyl ethyl ketoxime > DMP. Gelation test was conducted by using the isocyanate adducts with hydroxyl functional aqueous polyurethane dispersion. It was also found that the dispersions of blocked adducts are stable and compatible with polyurethane (polyether and polyester based) and acrylic dispersions.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Surfaces, Coatings and Films
- Organic Chemistry
- Materials Chemistry