Method of activating and esterifying the surface of finely divided particles of silica having surface silanol groups

Claim 1

A PROCESS WHICH COMPRISES THE STEPS OF HEATING, AT A TEMPERATURE OF FROM 300 TO 800* C., A MATERIAL HAVING AN INTERNAL STRUCTURE OF AN INORGANIC, WATER-INSOLUBLE, SILICEOUS SOLID IN A SUPERCOLLOIDAL STATE OF SUBDIVISION HAVING A SPECIFIC SURFACE AREA OF AT LEAST 25 M.2/G. AND BEARING A SUFFICIENT PROPORTION OF SURFACE SILANOL GROUPS THAT THE HYDROXYLATED SURFACE AREA IS GREATER THAN 85% OF THE TOTAL SURFACE AREA, THE TIME OF HEATING BEING SUFFICIENT TO ACTIVATE THE SURFACE OF SAID SOLID AND REDUCE ITS SPECIFIC HYDROXYLATED SURFACE AREA TO LESS THAN 85 PERCENT OF ITS SPECIFIC SURFACE AREA, AND THEREAFTER CHEMICAL REACTING WITH THE ACTIVATED SOLID AN ALCOHOL OF THE FORMULA ROH, IN WHICH R IS A HYDROCARBON RADICAL HAVING FROM 2 TO 18 CARBON ATOMS WHEREIN THE CARBON ATTACHED TO OXYGEN IS ALSO ATTACHED TO HYDROGEN, THE SILICA BEING COOLED, PRIOR TO CONTACT WITH THE ALCOHOL, TO A TEMPERATURE BELOW THE THERMAL DECOMPOSITION TEMPERATURE OF THE ALCOHOL AND BEING MAINTAINED IN A DRY ATMOSPHERE AFTER THE ACTIVATION UNTIL CONTACT WITH THE ALCOHOL IS EFFECTED, SAID REACTION WITH ALCOHOL BEING EFFECTED AT A TEMPERATURE IN THE RANGE FROM 30* C. TO THE THERMAL DECOMPOSITION TEMPERATURE OF THE ALCOHOL AND WHILE THE WATER CONTENT OF THE REACTION SYSTEM IS MAINTAINED BELOW 3 PERCENT BY WEIGHT BASED ON THE ALCOHOL PRESENT AND BEING CONTINUED UNTIL THE PRODUCT IS SUFFICIENTLY ORGANOPHILIC THAT IT IS PREFERENTIALLY WETTED BY BUTANOL IN A BUTANOL-WATER MIXTURE.