水性双组分涂料用丙烯酸酯乳液的羟值因素

Effects of Hydroxyl Value on Properties of Two-Component Waterborne Polyurethane Coatings

以甲基丙烯酸-β-羟丙酯（HPMA）为羟基单体，采用种子乳液聚合、极性单体分段滴加工艺合成了高羟值（98．8mgKOH／g）和高固含量（≥45．0％）的丙烯酸酯乳液，配制水性双组分丙烯酸酯聚氨酯涂料（2K—WPU），考查了羟值对聚合稳定性、乳液粒径和涂膜物理化学性能的影响，研究了水性双组分丙烯酸酯聚氨酯涂料合适的-NCO和-0H物质量的比。研究发现：羟值的提高会增加乳液聚合的凝胶率，降低单体的转化率，使乳液聚合稳定性下降，乳液粒径变大，分布变宽；涂膜硬度和交联度随羟值的增大而提高，涂膜光泽和耐介质性能分别在羟值为65．9mgKOH／g和82．4mgKOH／g时达到最佳；当n（-NCO）：n（-OH）为1．5～1．8时，水性双组分丙烯酸酯聚氨酯涂膜的综合性能最佳。傅里叶红外光谱分析表明在涂膜形成过程中-NCO与-OH的固化反应完全需7d，TGA分析了水性双组分聚氨酯涂膜的耐热性。

The polyacrylate emulsion with high hydroxyl value （98.8 mgKOH/g） and high solid content （ ≥45.0% ） for two - component waterborne polyurethane coatings （2K WPU） were synthsized by semi - batch seed emulsion polymerization with β -hydroxypropyl methacrylate （HPMA） as a hydroxyl monomer, where polar monomers were added by stages. The effects of hydroxyl value on the emulsion polymerization stability, the particle sizes and distributions of latexes and cured film performances were investigated and the molar ratio of--NCO and --OH groups were also discussed. The results indicated that with increasing of hydroxyl value, the latex particle size and distributions of latexes increased and the emulsion polymerization stability decreased, gel content increased, monomer conversion rate decreated, while the crosslinking density and hardness of the cured films improved. The properties of cured films including water or alcohol resistance, gloss of the cured film were good when the hydroxyl value of polyacrylate emulsions were 65.9 mgKOH/g and 82.4 mgKOH/g respectivity. The optimum molar ratio of --NCO and --OH of 2K WPU were in the range of 1.5 - 1.8. The FT - IR spectra showed that the reactions between --NCO and --OH in the 2K WPU films lasted for 7 days. TGA curves indicated that the thermal stability of cured films were inferior to those of polyacrylate films.