Electrodeposition properties of self‐crosslinking epoxy–amine cationic resin modified by polycaprolactone diol

Abstract

AbstractA self‐crosslinking polycaprolactone diol (PCD)‐modified epoxy–amine adduct was prepared by first synthesizing the PCD‐modified epoxy resin from diglycidyl ether of bisphenol A (DGEBA), PCD and bisphenol A (BPA), then reacting the partially pendant hydroxyl groups of this modified resin with 2‐ethylhexanol half‐blocked with toluene diisocyanate (2‐EH half‐blocked TDI), and finally reacting the terminal epoxy groups with secondary amines such as N‐methyl ethanol amine (MEA) and di(2‐methylisobutylketimino‐ethyl)amine (DKI). This epoxy–amine adduct was neutralized by acetic acid and could be dispersed in deionized water to form a stable emulsion, which could be used for the electrodeposition coating. The effects of solid content, pH value, solvent content of the emulsion, bath temperature, and applied voltage on the deposition yield and the throwing power of the resin were investigated. Meanwhile, the optimum crosslinking condition of the deposition film was also studied. It was found that the electrodeposition properties of the emulsion derived from the modified epoxy resin are superior to those of emulsion derived from the unmodified DGEBA epoxy resin.