The invention relates to borosiloxane and a preparation method thereof. According to the method, a
hydrolysis solvent and a
boron compound are mixed proportionally and added to a reactor, the temperature keeps from 10 DEG C to 35 DEG C, and a mixed
monomer is slowly dropwise added under the stirring condition for a
hydrolysis reaction; the dropwise-adding time is controlled in 3-6 hours, the reactor is slowly heated to the temperature
ranging from 55 DEG C to 65 DEG C after the dropwise-adding is finished, a stirring reaction is performed for 1 hour, and still standing is performed;
acid water on the lower layer is separated and neutralized to be neutral, a saturated NaCl solution is used for washing, and an
oil phase material is obtained; reduced pressure
distillation is performed to remove the
solvent, a catalyst I is added, the mixture is heated to 110-130 DEG C, and the
rearrangement reaction is performed for 3-5 hours; the mixture is heated to 150-160 DEG C, the splitting cyclization reaction is performed for 2-5 hours, the reaction is finished, the mixture is cooled, and a polyborosiloxane
prepolymer is obtained; an end-capping
reagent and a catalyst II are added to a
system and heated to 110-130 DEG C, and react for 2-4 hours; and pressure is reduced to remove a low-boiling-point substance, and a polyborosiloxane resin is obtained. The borosiloxane and the preparation method have the advantages of good
temperature resistance,
ageing resistance,
impact resistance,
toughness and low-temperature flexibility,
high adhesion and the like.