Synthesis and characterization of a new compound bearing ketone and hydroxyl groups for preparation of ambient temperature self-crosslinking waterborne polyurethanes

A new crosslinker for polyurethane, N-[(1,1-dimethyl-2-acetyl)ethyl]-β-dihydroxy ethylamino propanamide (DDP), was synthesized by Michael reaction using diethanolamine (DEA) and diacetone acrylamide (DAAM). DDP is a dihydroxyl-containing compound with ketone moiety, which crosslinks during film formation through a reaction between ketone of DDP and hydrazide in water-soluble dihydrazide compound, added upon preparation of waterborne polyurethane. The optimal ratio of DEA/DAAM for Michael reaction, determined by gas chromatography (GC), was of 1.05 mol; highest yields (80%) were obtained with this ratio when the reaction was carried out at 90 °C with 12 h of reaction time using acetonitrile as solvent. Experimental conditions of DDP separation from the reaction mixture were predetermined first through thin-layer chromatography, and DDP separation was conducted by column chromatography. DDP with 97% of purity or higher was obtained. The structure of DDP was fully characterized by IR and NMR. The elemental composition and molecular weight of DDP were confirmed by high resolution GC–MS and HPLC–MS, respectively. Polyurethane latexes with DDP and post-added dihydrazide were prepared, and polymer film properties compared with DDP-free latex film. Tensile strength increased with a decrease in elongation in crosslinked polymers. Higher performance in water and solvent adsorptions was also detected.