Preparation method of modified silica sol for sapphire polishing

The preparation method of the modified silica sol for sapphire polishing comprises the following steps: dispersing a silane coupling agent in an alcohol/water mixed solution containing a catalyst to obtain a silane coupling agent hydrolysis medium solution; the method comprises the following steps: dispersing pure water, a catalyst and alcohol in a reactor to obtain mother liquor; the preparation method comprises the following steps: dispersing high-purity organosilane in alcohol to obtain a mixed solution; slowly and dropwise adding the mixed solution into the mother solution, and continuously stirring at a constant speed to react for two hours after finishing feeding, so as to obtain a silica sol stock solution; and slowly adding the hydrolysis medium solution into the silica sol stock solution, continuously stirring for 2 hours, adding a proper amount of pure water, heating at low pressure, evaporating, concentrating and recovering the alcohol solvent and the catalyst, and adjusting the pH value of the res