Surface-treated metal oxide particles

Abstract

The invention provides metal oxide particles surface-treated with at least one alkoxysilane compound, methods of making such, and toners comprising same.

1 .- 23 . (canceled) 
     
     
         24 . A method of preparing hydrophobic metal oxide particles comprising
 (a) providing an aqueous dispersion of hydrophilic metal oxide particles,   (b) combining the dispersion with at least one alkoxysilane treating agent to provide a reaction mixture, wherein the reaction mixture is basic, and   (c) drying the reaction mixture to provide hydrophobic metal oxide particles having a tap density of about 110 g/l to about 420 g/l or less and a BET surface area of about 200 m 2 /g or less.   
     
     
         25 . The method of  claim 24 , wherein the at least one alkoxysilane compound is octyltriethoxysilane. 
     
     
         26 . The method of  claim 24 , wherein the metal oxide particles are treated with two alkoxysilane compounds. 
     
     
         27 . The method of  claim 26 , wherein the two alkoxysilane compounds are octyltriethoxysilane and 3-aminopropyltriethoxysilane. 
     
     
         28 . The method of  claim 24 , wherein the particle size of the hydrophobic metal oxide particles is reduced after the reaction mixture is dried. 
     
     
         29 . The method of  claim 24 , wherein the dispersion is prepared by mixing a metal oxide dispersion with water and then with a water-soluble organic solvent. 
     
     
         30 . The method of  claim 29 , wherein the water-soluble organic solvent to water volume ratio is about 0.2 to about 2. 
     
     
         31 . The method of  claim 24 , wherein the reaction mixture is maintained at a temperature of about 45° C. to about 75° C. for about 1 hour or longer. 
     
     
         32 . The method of  claim 24 , wherein the dispersion comprises about 10 wt. % to about 25 wt. % metal oxide particles. 
     
     
         33 . The method of  claim 24 , wherein the metal oxide particles are non-aggregated metal oxide particles. 
     
     
         34 . The method of  claim 24 , wherein the metal oxide particles are colloidal silica particles. 
     
     
         35 . A method of preparing hydrophobic metal oxide particles comprising
 (a) providing an aqueous dispersion of non-aggregated hydrophilic metal oxide particles,   (b) combining the dispersion with at least one alkoxysilane treating agent to provide a reaction mixture, wherein the reaction mixture is basic,   (c) drying the reaction mixture to provide hydrophobic metal oxide particles, and   (d) reducing the agglomerate size of the hydrophobic metal oxide particles by jet milling or hammer milling.   
     
     
         36 . The method of  claim 35 , wherein the metal oxide particles have a tap density of about 110 g/l to about 420 g/l. 
     
     
         37 . The method of  claim 35 , wherein the metal oxide particles are colloidal silica particles.