Toner additives comprising composite particles

1. A toner composition comprising toner particles mixed with a powder comprising metal oxide-polymer composite particles comprising metal oxide particles and a polymer matrix, wherein:

the metal oxide particles are surface-modified with a first hydrophobizing agent via which the metal oxide particles are covalently attached to the polymer matrix, and

a portion of the metal oxide particles project into and out from the polymer matrix, wherein

the polymer matrix comprises a polymer or copolymer of the first hydrophobizing agent, and

the first hydrophobizing agent has the formula [R 3 3-x (OR 1 ) x ]SiR 2 Q, where x is 1, 2, or 3 R 1 is methyl or ethyl, R 2 is an alkyl linker with the general formula C n H 2n , where n=1-10, R 3 is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate ester, or methacrylate ester group, with the proviso that when Q is substituted or unsubstituted vinyl, n is 2-10.

2. The toner composition of claim 1 , wherein the surface of the metal oxide particles is modified with a second hydrophobizing agent, wherein the second hydrophobizing agent is selected from silazane compounds, siloxane compounds, silane compounds, and silicone fluids having a number average molecular weight of at most 500.

3. The toner composition of claim 1 , wherein the metal oxide-polymer composite particles are treated with a third hydrophobizing agent, wherein the third hydrophobizing agent is an alkylhalosilane or a silicone fluid having a number average molecular weight greater than 500.

4. The toner composition of claim 1 , wherein the polymer comprises polymers of styrene, unsubstituted or substituted acrylates or methacrylates, olefins, vinyl esters, and acrylonitrile and copolymers and mixtures of the above.

5. The toner composition of claim 1 , wherein when the metal oxide-polymer composite particles are combined with polyester chemical toner particles having a particle size from 8-12 μm to form a toner having 4 wt % metal oxide-polymer composite particles and the toner combined with silicone coated Cu—Zn ferrite carrier having a particle size from 60-90 μm to form a mixture having 2 wt % toner and the mixture agitated rhythmically in a container with a fill factor from about 70% to about 90% in a three-dimensional mixer within a volume about 6 to about 8 times the volume of the container for 10 minutes at a frequency from about 50 to about 70 cycles/min, their diameter increases by less than 25%.

6. The toner composition of claim 1 , wherein the moisture content of the metal oxide-polymer composite particles is from 0 wt % to about 10 wt % when measured after equilibration at 50% relative humidity and 25° C. at about 1 atm pressure.

7. A toner composition comprising toner particles mixed with a powder comprising metal oxide-polymer composite particles comprising metal oxide particles and a polymer matrix, wherein:

the metal oxide particles are surface-modified with a first hydrophobizing agent via which the metal oxide particles are covalently attached to the polymer matrix and wherein at least a portion of the surface of the metal oxide-polymer composite particles is modified with a second hydrophobizing agent, wherein the polymer of the polymer matrix is a polymer or co-polymer of the first hydrophobizing agent, wherein the first hydrophobizing agent has the formula [R 3 3-x (OR 1 ) x ]SiR 2 Q, where x is 1, 2, or 3, R 1 is methyl or ethyl, R 2 is an alkyl linker with the general formula C n H 2n , where n=1-10, R 3 is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate ester, or methacrylate ester group, with the proviso that when Q is substituted or unsubstituted vinyl, n is 2-10.

8. The toner composition of claim 7 , wherein a portion of the metal oxide particles are partially or fully embedded within the polymer portion of the metal oxide-polymer composite particles.

9. The toner composition of claim 7 , wherein the metal oxide-polymer composite particles have an average roughness P 2 /4πS from 1 to about 3, where P is a perimeter of a cross-section of a metal oxide-polymer composite particle and S is the cross-sectional area of the particle and where both P and S are determined from transmission electron micrographs.