Plant-oil-based asphalt modifier, modified asphalt containing modifier and preparation of plant-oil-based asphalt modifier

The invention discloses a plant-oil-based polyurethane modifier, modified asphalt and a preparation method of the plant-oil-based asphalt modifier. According to the plant-oil-based polyurethane modifier, dehydrated plant oil polyalcohol replaces petroleum-based polyalcohol to serve as a polyhydroxy component, the polyhydroxy component is added into a polyisocyanate component at the temperature of 25-35 DEG C, the index R of isocyanate ranges from 1.4 to 1.8, the temperature is raised to 40-50 DEG C after the polyhydroxy component is added, a heat preservation reaction is carried out for 1.5-3 h, a solvent with the volume accounting for 5-50% of the total volume of the reactant is added in the reaction process to adjust the system viscosity, and a series of plant-oil-based polyurethane prepolymers with different condensation degrees are prepared. The synthesis degree of the prepolymers is controlled, the prepolymers are added into matrix asphalt, and the modified asphalt containing plant-oil-based polyurethane is prepared. The asphalt modifier is low in viscosity and good in fluidity, and is easily dispersed in asphalt, the temperature needed by the shear process is low, time is short, the prepared plant-oil-based polyurethane modifier is environmentally friendly and renewable, and the obtained modifier asphalt is simple in ingredient and excellent in high and low temperature performance.