Add 1 mol of castor oil to the reactor and add 0.3% of solid potassium hydroxide equivalent to the mass of castor oil. Stirring was done and the temperature was raised until the KOH was dissolved. Then the air in the kettle was displaced with N2. The reaction temperature was maintained at 160～180 ℃ and the pressure was 0.15～0.2 MPa. After the passage, stirring was continued until the pressure no longer decreased. Cooling. Move the material into the bleaching kettle, adjust the pH to slightly acidic with acetic acid, add 0.1% hydrogen peroxide to decolorize, keep warm at 70 ℃ for 0.5 h. Finally, dehydrate under reduced pressure for 5 h. Cool the material. The reaction formula is as follows .