The Synthesis And Moddification Research Of Water-Based Electrophoretic Polyurethane Resins

In this dissertation, the synthesis and modification of water-based polyurethaneresins and their properties were studied. The dissertation consists of four main parts asfollow:The first part, the preparation of water-based cationic polyurethane and itsdispersion were studied. The effect of process variables such as contents of MDEA,diisocyanates, polyols, initial NCO/OH(R index) on the performance of water-basedpolyurethane resin and the electrophoretic film was discussed. The results showed thatthe particle size and storage stability of PU dispersion were determined by the contentof MDEA, the hardness of film became harden with an increasing in R (NCO/OH)index, the performance of electrophoretic film synthesized by IPDI and polyester wasbetter than that of PU dispersion from the other raw material.The second part, the properties of semi-blocked TDI grafted cationic acrylic resinwere studied. Hydric-acrylic resin was synthesized by free radical copolymerization,and then the acrylic resins modified by PU were prepared from the hydric-acrylicresin and semi-blocked TDI by MEKO. Isocyanate cross-linking cationic acrylicresins was carried out by the reaction of the NCO group of TDI with the hydroxylgroup of the hydric-acrylic resin at high temperature. The results showed that with anincrease in the crosslinked density, the Tg and gel-content increased gradually. Thecorrosion resistance, water-proof capability and the mechanic properties were alsoimproved.The third part, UV curing water-based polyurethane resin was synthesized. The resinwas prepared from the reaction of the NCO group of PU prepolymer with OH groupof HEA compound. The properties of the UV cured resin were studied. The resultsshowed that with an increase in the content of blocking agent (HEA), the Tg, hardnessand gel-content of the cured PU resin increased gradually, whereas both emulsion dispersibility and storage stability became worse. The acid or alkali resistance,water-proof ability and the mechanic properties were all improved much.The fourth part, in order to improve the poor corrosion resistance ability andincrease the thickness of electrophoretic film, the epoxy resin was employed tomodify the molecule chain of polyurethane resin. The satisfied electrophoretic filmswere obtained and the performance of the film were improved much. The modifiedresult of E-12 was superior to that of E-44, and when the neutralization degree of themodified PU resin was about 80ï¼…, the film from the PU dispersion was desired.