Hydrophobic-treated metal oxide

Abstract

This invention provides metal oxide particles surface-treated with a hydrophobicity-imparting agent, methods of making such, and toner compositions comprising the same.

1 . A particle composition comprising metal oxide particles surface-treated with a first hydrophobicity-imparting agent, which metal oxide particles are hydrophobic, non-aggregated, and contain substantially no free alkali metal cations. 
     
     
         2 . The composition of  claim 1 , wherein the first hydrophobicity-imparting agent is an alkoxysilane compound selected from the group consisting of monoalkoxysilane compounds, dialkoxysilane compounds, and trialkoxysilane compounds. 
     
     
         3 . The composition of  claim 2 , wherein the first hydrophobicity-imparting agent is a trialkoxysilane compound. 
     
     
         4 . The composition of  claim 3 , wherein the trialkoxysilane compound is octyltriethoxysilane. 
     
     
         5 . The composition of  claim 1 , wherein the metal oxide particles are surface-treated with a second hydrophobicity-imparting agent. 
     
     
         6 . The composition of  claim 5 , wherein the second hydrophobicity-imparting agent is an aza-silane. 
     
     
         7 . The composition of  claim 5 , wherein the second hydrophobicity-imparting agent is an aminoalkylsilane. 
     
     
         8 . The composition of  claim 5 , wherein the second hydrophobicity-imparting agent is hexamethyldisilazane. 
     
     
         9 . The composition of  claim 1 , wherein the metal oxide particles have an average particle size of about 300 nm or less. 
     
     
         10 . The composition of  claim 1 , wherein the metal oxide particles have a BET surface area of about 200 m 2 /g or less. 
     
     
         11 . The composition of  claim 10 , wherein the metal oxide particles have a BET surface area of about 80 m 2 /g or less. 
     
     
         12 . The composition of  claim 1 , wherein the metal oxide particles are in the form of a dry powder. 
     
     
         13 . The composition of  claim 1 , wherein the metal oxide particles have a tap density of about 75 g/L to about 650 g/L. 
     
     
         14 . The composition of  claim 1 , wherein the metal oxide particles have a tap density of about 290 g/L to about 650 g/L. 
     
     
         15 . The composition of  claim 1 , wherein the metal oxide particles have a true density of about 1.7 g/cm 3  to about 2.0 g/cm 3 . 
     
     
         16 . The composition of  claim 1 , wherein the metal oxide particles have a true density of about 2.0 g/cm 3  to about 2.3 g/cm 3 . 
     
     
         17 . The composition of  claim 1 , wherein a solid-state Si nuclear magnetic resonance spectrum of the metal oxide particles exhibits a ratio T3:T2 of about 0.4 to about 10, wherein T2 is the intensity of a peak having a chemical shift in the CP/MAS 29 Si NMR spectrum centered within the range of −56 ppm to −59 ppm, and wherein T3 is the intensity of a peak having a chemical shift in the CP/MAS 29 Si NMR spectrum centered within the range of −65 ppm to −69 ppm. 
     
     
         18 . The composition of  claim 1 , wherein the metal oxide particles are colloidal silica particles. 
     
     
         19 . The composition of  claim 18 , wherein the colloidal silica particles are prepared from an alkali silicate. 
     
     
         20 . A toner composition comprising toner particles and metal oxide particles surface-treated with a first hydrophobicity-imparting agent, which metal oxide particles are hydrophobic and contain substantially no free alkali metal cations. 
     
     
         21 . The toner composition of  claim 20 , wherein the metal oxide particles are non-aggregated. 
     
     
         22 . The toner composition of  claim 20 , wherein the first hydrophobicity-imparting agent is an alkoxysilane compound selected from the group consisting of monoalkoxysilane compounds, dialkoxysilane compounds, and trialkoxysilane compounds. 
     
     
         23 . The toner composition of  claim 20 , wherein the first hydrophobicity-imparting agent is a trialkoxysilane compound. 
     
     
         24 . The toner composition of  claim 23 , wherein the trialkoxysilane compound is octyltriethoxysilane. 
     
     
         25 . The toner composition of  claim 20 , wherein the metal oxide particles are surface-treated with a second hydrophobicity-imparting agent. 
     
     
         26 . The toner composition of  claim 25 , wherein the second hydrophobicity-imparting agent is an aza-silane. 
     
     
         27 . The toner composition of  claim 25 , wherein the second hydrophobicity-imparting agent is an aminoalkylsilane. 
     
     
         28 . The toner composition of  claim 25 , wherein the second hydrophobicity-imparting agent is hexamethyldisilazane. 
     
     
         29 . The toner composition of  claim 20 , wherein the metal oxide particles have an average particle size of about 300 nm or less. 
     
     
         30 . The toner composition of  claim 20 , wherein the metal oxide particles have a BET surface area of about 200 m 2 /g or less. 
     
     
         31 . The toner composition of  claim 30 , wherein the metal oxide particles have a BET surface area of about 80 m 2 /g or less. 
     
     
         32 . The toner composition of  claim 20 , wherein the metal oxide particles have a tap density of about 75 g/L to about 650 g/L. 
     
     
         33 . The toner composition of  claim 20 , wherein the metal oxide particles have a tap density of about 290 g/L to about 650 g/L. 
     
     
         34 . The toner composition of  claim 20 , wherein the metal oxide particles have a true density of about 1.7 g/cm 3  to about 2.0 g/cm 3 . 
     
     
         35 . The toner composition of  claim 20 , wherein the metal oxide particles have a true density of about 2.0 g/cm 3  to about 2.3 g/cm 3 . 
     
     
         36 . The toner composition of  claim 20 , wherein the metal oxide particles are colloidal silica particles. 
     
     
         37 . The toner composition of  claim 36 , wherein the colloidal silica particles are prepared from an alkali silicate. 
     
     
         38 . The toner composition of  claim 20 , wherein a solid-state Si nuclear magnetic resonance spectrum of the metal oxide particles exhibits a ratio T3 :T2 of about 0.4 to about 10, wherein T2 is the intensity of a peak having a chemical shift in the CP/MAS 29 Si NMR spectrum centered within the range of −56 ppm to −59 ppm, and wherein T3 is the intensity of a peak having a chemical shift in the CP/MAS 29 Si NMR spectrum centered within the range of −65 ppm to −69 ppm. 
     
     
         39 . A method of preparing hydrophobic metal oxide particles comprising
 (a) providing an aqueous dispersion of metal oxide particles, wherein the aqueous dispersion is acidic or basic,   (b) combining the dispersion with a first hydrophobicity-imparting agent to provide a reaction mixture, and   (c) drying the reaction mixture to provide hydrophobic metal oxide particles, wherein the hydrophobic metal oxide particles contain substantially no free alkali metal cations.   
     
     
         40 . The method of  claim 39 , wherein the hydrophilic metal oxide particles are non-aggregated. 
     
     
         41 . The method of  claim 39 , wherein the first hydrophobicity-imparting agent is an alkoxysilane compound selected from the group consisting of monoalkoxysilane compounds, dialkoxysilane compounds, and trialkoxysilane compounds. 
     
     
         42 . The method of  claim 41 , wherein the first hydrophobicity-imparting agent is a trialkoxysilane compound. 
     
     
         43 . The method of  claim 42 , wherein the trialkoxysilane compound is octyltriethoxysilane. 
     
     
         44 . The method of  claim 39 , wherein part (b) further comprises combining the dispersion with a second hydrophobicity-imparting agent. 
     
     
         45 . The method of  claim 44 , wherein the second hydrophobicity-imparting agent is an aza-silane. 
     
     
         46 . The method of  claim 44 , wherein the second hydrophobicity-imparting agent is an aminoalkylsilane. 
     
     
         47 . The method of  claim 44 , wherein the second hydrophobicity-imparting agent is hexamethyldisilazane. 
     
     
         48 . The method of  claim 39 , wherein the agglomerate particle size of the hydrophobic metal oxide particles is reduced after the dispersion is dried. 
     
     
         49 . The method of  claim 39 , wherein the dispersion is prepared by mixing an aqueous metal oxide dispersion with a water-miscible organic solvent, before contacting the metal oxide particles with the first hydrophobicity-imparting agent. 
     
     
         50 . The method of  claim 44 , wherein the dispersion is prepared by mixing an aqueous metal oxide dispersion with a water-miscible organic solvent, before contacting the metal oxide particles with the second hydrophobicity-imparting agent. 
     
     
         51 . The method of  claim 50 , wherein the organic solvent to water volume ratio is between about 0.2 and about 2. 
     
     
         52 . The method of  claim 39 , wherein the reaction mixture is maintained at a temperature between about 40° C. and about 80° C. for about 1 hour or longer. 
     
     
         53 . The method of  claim 39 , wherein the dispersion comprises between about 10 wt. % and about 45 wt. % metal oxide particles. 
     
     
         54 . The method of  claim 39 , wherein the metal oxide particles are colloidal silica particles. 
     
     
         55 . The method of  claim 54 , wherein the colloidal silica particles are prepared from an alkali silicate.