Preparation and Characterization of Low-gloss Waterborne Polyurethane Coatings

摘要

In this research, a series of anionic low-gloss waterborne polyurethanes were prepared, and their surface structures were studied. Samples were prepared with terminal hydroxyl polydimethylsiloxane (PDMS), polyethylene glycol (PEG) of different molecular weight, toluene diisocyanate (TDI), dimethylolpropionic acid (DMPA), in the presence of dibutyltin dilaurate (DBTDL) catalyst, neutrallized by triethylamine (TEA). Preparation process was optimized to get better emulsion stability and matting effect of coating. The preparation process is: at 90°C, react terminal hydroxyl polydimethylsiloxane, polyethylene glycol, toluene diisocyanate and dibutyltin dilaurate catalyst together for 4h. Cool the performed polymer to 50°C, then add quantified dimethylolpropionic acid and solvent such as tetrahydrofuran, heat to 70°C and react for 2h. Cool polymer to room temperature, add quantified triethyl-amine and deionized water to make emulsions. Matting aqueous polyurethane under the conditions of R = 1.2, DMPA mass fraction of 6%, PEG molecular weight of 1000, PEG/PDMS molar ratio = 1: 3, catalyst mass fraction of 0.5%, neutralization degree 100%, latex solid content of 20%, gets the best overall performance, 60° gloss of 3.3, in line with matting standards.