Microcapsule, self-healing electrophoretic coating containing microcapsule and preparation method of microcapsule

[0032] Example 1 Preparation of main resin

[0033]

[0034] *Prepared by reacting diethylenetriamine and methyl isobutyl ketone in a molar ratio of 1:2, the solid content of the final product is 73%

[0035] In a reaction flask equipped with a thermometer, a stirrer and a reflux condenser, add the formula amount of E51 epoxy resin, bisphenol A and the first part of methyl isobutyl ketone in sequence. After the addition is complete, start stirring and heat the reaction system to 120°C and keep it warm. After adding triphenylphosphine, raise the temperature to 150°C, and continue the reaction at this temperature for 1 hour. When the epoxy equivalent of the reaction system reaches the theoretical value (EEW =1140.5), start to cool down; when the system temperature drops below 100°C, add N-methylethanolamine and ketimine, and the second part of methyl isobutyl ketone into the reaction system, and then raise the temperature to 120°C again, The reaction was continued at this temperature for 2 hours; after the reaction, the temperature of the reaction system was lowered to 70° C. to obtain the main resin with a final solid content of 85.0%.

[0036] Example 2 Preparation of curing agent

[0037]

[0038] Add the formula amount of 4,4`-diphenylmethane diisocyanate and dibutyltin dilaurate into the reaction flask equipped with thermometer, stirrer and reflux condenser, stir and warm up to 60℃, then start to add glycol mono For butyl ether, reduce the temperature in a water bath during the dripping process and control the temperature to not exceed 65°C. After the dripping is completed, continue to react at 80°C for 2h. Use standard di-n-butylamine back titration to analyze the remaining isocyanate group content in the reaction system. When the remaining isocyanate group content is less than 0.2%, methyl isobutyl ketone is added to dilute to obtain a fully blocked isocyanate crosslinking agent with a final solid content of 80%.

[0039] Example 3 Preparation of microcapsules

[0040] In a four-necked flask equipped with a thermometer, a stirrer and a reflux condenser, 296 g of E51 epoxy resin (EEW ​​= 185), 106 g of bisphenol A, 45 g of methyl isobutyl ketone, and 0.6 g of triphenyl phosphine were sequentially added, and the temperature was increased. After 145-155℃, heat preservation for 2h, after measuring epoxy equivalent 670, add 126g silane coupling agent KH-550, 86g methyl isobutyl ketone, react for 2 hours, reaction temperature 120-125℃, then vacuum dry and Keep sealed. Add 30 g of urea and 150 g of 37% formaldehyde into a four-necked flask, stir and mix thoroughly, then adjust the pH to 8.0-9.0 with triethanolamine, and raise the temperature to 70° C. until all are dissolved to obtain a colorless and transparent prepolymer. Then cool to room temperature, add 3g of ammonium chloride, 4g of resorcinol, 3.5g of sodium chloride and 1.3g of OP-10 emulsifier to the prepolymer. After stirring and dissolving completely, adjust the pH to 7.0 with triethanolamine. Then add KH-550 modified epoxy resin, stir 500r/min, emulsify for 1h; then adjust the pH to 3 with dilute hydrochloric acid, and slowly raise the temperature to 60℃, keep it for 2h, after the reaction, wash and filter , Dry to obtain powdery microcapsules.