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 non-aggregated hydrophilic metal oxide particles,   (b) combining the dispersion with at least one alkoxysilane treating agent to provide a reaction mixture, the reaction mixture comprising not more than about 40 wt % of water-soluble organic solvent, wherein the reaction mixture is basic, and   (c) drying the reaction mixture to provide non-aggregated 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 . (canceled) 
     
     
         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, the reaction mixture comprising not more than about 40 wt % of water-soluble organic solvent wherein the reaction mixture is basic,   (c) drying the reaction mixture to provide non-aggregated 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.