An improved aqueous cathodic electrocoating composition that contains an anti-crater agent which is a water-reducible polyester resin having an acid value less than 40 mg KOH/g. The water-reducible polyester is the reaction product of (1) a hydroxy cyclic carbonate; (2) a polycarboxylic acid anhydride; (3) optional monofunctional epoxy resin; (4) a polyfunctional isocyanate resin; and, (5) a polyamine compound containing tertiary amine and either primary or secondary functionality. The reaction product is neutralized in the presence of acid and water to convert the tertiary amine groups to water-dilutable groups. Hydrolyzable silane groups can also be incorporated into the reaction product to further enhance its crater resistance property. The electrocoat composition produces coatings having a smoother appearance with fewer craters without adversely affecting intercoat adhesion of the cured film to subsequent coating layers applied thereover.
一种改进的
水性阴极电涂层组合物,其中含有一种防缩孔剂,它是一种酸值小于 40 毫克 KOH/g 的
水溶性聚酯
树脂。该
水还原性聚酯是以下物质的反应产物:(1) 环
碳酸羟酯;(2) 聚
羧酸酐;(3) 任选的单官能环氧
树脂;(4) 多官能
异氰酸酯树脂;以及 (5) 含有叔胺和
伯胺或仲胺官能团的
多胺化合物。反应产物在酸和
水的存在下进行中和,将叔胺基团转化为可稀释的
水基。可
水解
硅烷基团也可加入反应产物中,以进一步增强其抗缩孔性能。这种电涂层组合物生产出的涂层外观更平滑,凹坑更少,同时不会对固化薄膜与后续涂层的层间附着力产生不利影响。