Studies On Synthesis And Properties Of Polyether-type Isocyanate Curing Agent

In this paper, first, acetone oxime was synthesized with hydroxylamine hydrochloride and acetone in the ethanol solvent. pH value was adjusted by pyridine, and the solvent was ethanol.The react product was under-pressure distilled to remove solvent. The optimal condition was also given. Methyl ethyl ketoxime was synthesized too.Prepolymers were then synthesized with Polyether diol and Methylene bis(4-phenylene isocyanate) (MDI). Blocked isocyanated curing agents were synthesized with acetone oxime, methyl ethyl ketoxime, dimethylglyoxime and nitromethane as blocking agent respectively. Blocking and deblocking mechanisms of isocyanate curing agents for electrophoretic coatings was introduced. The influences of reaction temperature, reaction time, feeding mode and prepolymer molar ratio on blocking reaction of iscoyanate were investigated. The release reaction of blocked prepolymer were discussed and release temperature were determined .The structures of preploymers and isocyanate curing agents were characterized by Chem-titrimetry, IR spectrum and DSC. The result revealed that deblocking temperature was low when blocked by methyl ethyl ketoxime.The low temperature deblocking isocyanate curing agents and amino modified epoxy system were used for preparing low temperature curable cathodic electrophoretic coatings. Properties of the obtaind electrophoretic coatings were tested. The result indicated that the properties of the product were very well. Such as curable at low temperature, electrophoresis throwing power, good water resistance, high softness and high Corrosion resistance.