Synthetic method of castor oil based enclosed type waterborne polyurethane

The invention belongs to the technical field of chemical synthesis, and particularly relates to a synthetic method of castor oil based enclosed type waterborne polyurethane. The synthetic method comprises steps as follows: castor oil, polyethylene glycol and a hydrophilic chain extender are adopted to react with diisocyanate in a hydrophilic solvent, and a polyurethane prepolymer with a terminal NCO group is obtained; a sealing agent is adopted to be in an end capping reaction with the prepolymer, and an enclosed type polyurethane prepolymer is obtained; finally, after the enclosed type polyurethane prepolymer is in a neutralization reaction with a neutralizer, a product is dispersed in deionized water, and castor oil based enclosed type waterborne polyurethane is obtained. The adopted castor oil is an important renewable resource, and enclosed type waterborne polyurethane synthesized with the castor oil as a raw material has the characteristic of high self-crosslinking; a polyurethane coating prepared from the product has better heat resistance, volume resistivity, tensile strength and breaking elongation.