关键词: 水性UV光固化, 高固体份, 水稀释型, 聚氨酯丙烯酸酯, 黏度, 合成, 水溶液

Abstract:

In order to further reduce the water content in the UV-curable aqueous oligomers, the water-diluted polyurethane acrylate (WPUA) oligomer was synthesized using toluene diisocyanate as hard segment, polyether polyol and polyethyleneglycol as soft segments, dimethylol propionic acid (DMPA) as hydrophilic reactant, hydroxyl propyl acrylate and pentaerythritol triacrylate as end-capping reagent, and triethylamine as neutralizer. The solid contents of the oligomer were about 80%. The influence of types and molecular weight of soft segments, the molar ratio of -NCO/-OH, the addition sequence and amount of DMPA, and the amount of inner crosslinking agent and COOH on the viscosity and film properties of UV-curable oligomer was investigated. The prepared products were characterized by UV curing, tensile strength tests, FTIR, GPC and other analysis. The results showed that the COOH content was not only the factor influencing the viscosity of the oligomer. The diols of small molecular weight, the value of n(-NCO):n(-OH) between 1.7 and 1.8, DMPA concentration in hard segments or soft segments, and 15% of trimethylolpropane were more favorable to reduced viscosity. An optimum synthesis result was obtained when the pencil hardness was H, the bending flexibility was 2 mm, the fastest curing time was 2 s, the largest tensile strength was 11.88 MPa, and the largest elongation was 21.4%. More than 60% of water content was reduced by the waterborne UV-curable coatings as compared with similar products sold in the market. Thus, this UV-curable WPUA can be apply to reduce both the humidity and time requirements.

Key words: waterborne UV-curable, high solid content, water-diluted, polyurethane acrylate, viscosity, synthesis, aqueous solution