低温固化环氧阴极电泳涂料的大分子交联剂的制备

首先以聚乙二醇200(PEG-200)、异佛尔酮二异氰酸酯(IPDI)、二羟甲基丙酸(DMPA)为原料合成了末端为异氰酸根(—NCO)的预聚体,再以N-甲基二乙醇胺(MDEA)为封端剂对—NCO进行全封端反应。通过添加适量的亲水性DMPA,提高了封端大分子的自乳化性能,制备出全封闭型异氰酸酯大分子(P-M-I)乳液,以其作为环氧阴极电泳漆低温固化的交联剂。应用FT-IR、DSC、TG、TEM、粒径分析等检测手段对全封闭型大分子及其乳液进行了结构与性能表征。将其与胺化环氧树脂乳液进行共混,制备了低温固化环氧阴极电泳涂料。通过电泳涂装的金属样片在124～130℃烘烤30 min可完全固化成膜。实验结果表明:该大分子交联剂显著降低了电泳涂料的固化温度,涂膜外观平整光亮、附着力好、铅笔硬度达2H,综合性能良好。

Synthesis of Macromolecular Crosslinker for Epoxy Cathodic Electrophoretic Paint Curable at Low Temperature

A prepolymer terminated with isocyanate(NCO) was first synthesized with polyethylene glycol-200(PEG-200),isophorone diisocyanate(IPDI) and dimethylolpropionic acid(DMPA).Then methyldiethanolamine(MDEA) was used to block —NCO groups.In order to improve the self-emulsifying capability of the blocked macromolecule,a small amount of hydrophilic dimethylolpropionic acid(DMPA) was added to prepare fully blocked isocyanate macromolecular(P-M-I) emulsion,which was used as the crosslinker for epoxy cathodic electrophoresis paint curable at low temperature.The performance of P-M-I and its emulsion were characterized by IR,DSC,TGA and Zetasizer.The P-M-I emulsion and amine-epoxy resin emulsion were mixed by physical blending to prepare the epoxy cathodic electrophoretic coating curable at low temp.Under the baking schedure of 124~130 ℃/30 mins,the electrophoretic coatings on the metal panel can be cured completely.The results showed that the P-M-I could decrease the curing temperature of cathodic electrophoretic paint significantly.The coating film showed smooth appearance and good adhesion,hardness 2H and a better comprehensive properties.