Composite pigments

Abstract

There is provided a paint formulation comprising a composite pigment, said composite pigment being selected from the group consisting of metal oxide/silica, metal oxide/silicate, metal oxide/alumina, metal oxide/metal oxide and metal oxide/zirconia, wherein the size and amount of said composite pigment are selected to increase the opacity of said paint formulation.

1 .- 10 . (canceled) 
     
     
         11 . A composite pigment configured to increase opacity of a paint formulation, the paint formulation comprising a metal oxide as a first component and a second component selected from the group consisting of silica, silicate, and a metal oxide;
 the metal oxide of the first component being selected from the group consisting of zinc oxide, aluminum oxide, antimony oxide, barium oxide, magnesium oxide, and zirconium oxide;   the metal oxide of the second component, when present, being selected from the group consisting of zinc oxide, aluminum oxide, antimony oxide, barium oxide, magnesium oxide, and zirconium oxide;   the metal oxide of the first component being at least partially covered by the second component;   a particle size of the metal oxide in the first component being in a range of 5 nm to 100 nm;   the composite pigment having a particle size effective to provide opacity to the pigment and a specific surface area in a range of from 20 m 2 /g to 100 m 2 /g; and   at least one of:
 the composite pigment comprising a mixture of nanorods and multifaceted morphology; and 
 the composite pigment comprising a hollow core-shell structure. 
   
     
     
         12 . The composite pigment of  claim 11 , wherein the composite pigment comprises a mixture of nanorods and multifaceted morphology. 
     
     
         13 . The composite of  claim 11 , wherein the composite pigment comprises a hollow core-shell structure. 
     
     
         14 . The composite pigment of  claim 13 , wherein a shell of the hollow core-shell structure is formed of alternating layers of the first and second components. 
     
     
         15 . A method of preparing the composite pigment of  claim 11 , comprising:
 providing a metal salt as a first component precursor, the metal salt being selected from a zinc salt, an antimony salt, a barium salt, a magnesium salt, and a zirconium salt;   providing a second component precursor selected from a silica precursor and an alumina precursor;   providing a base solution selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide;   reacting the first component precursor, the second component precursor, and the base solution to form a reaction mixture; and   adjusting a pH of the reaction mixture to be in a range of 7-10 to form the composite pigment of  claim 11 .   
     
     
         16 . The method of  claim 15 , further comprising:
 adding a surfactant or dispersant to a solution comprising the first component precursor to reduce particle size of the first component to a nano-range size.   
     
     
         17 . The method of  claim 15 , further comprising:
 filtering or centrifuging the reaction mixture to separate the composite pigment;   washing the separated composite pigment; and   drying the separated composite pigment.   
     
     
         18 . A method of preparing the composite pigment of  claim 11 , comprising:
 (a) mixing a metal salt and a base solution to form a first component, which is a metal oxide;   (b) adding a second component to the metal oxide of step (a) to form a reaction mixture; and   adjusting a pH of the reaction mixture to be in a range of 7-10 to form the composite pigment of  claim 11 ;   the base solution being selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide;   the second component being selected from the group consisting of a silica, a silica precursor, an alumina, an alumina precursor, a metal oxide, and a metal oxide precursor;   the metal oxide in the first component being selected from the group consisting of zinc oxide, aluminum oxide, antimony oxide, barium oxide, magnesium oxide, and zirconium oxide;   the metal oxide precursor in the second component, when present, being selected from the group consisting of a zinc salt, an antimony salt, a barium salt, a magnesium salt, and a zirconium salt; and   the metal oxide in the second component, when present, being selected from the group consisting of zinc oxide, antimony oxide, barium oxide, magnesium oxide, and zirconium oxide.   
     
     
         19 . The method of  claim 18 , further comprising:
 adding an amine surfactant to the metal oxide obtained in step (a) to create a charge on the first component before step (b).   
     
     
         20 . The method of  claim 18 , further comprising:
 adding a surfactant or dispersant to a solution comprising the first component precursor to reduce particle size of the first component to a nano-range size.   
     
     
         21 . The method of  claim 18 , further comprising:
 filtering or centrifuging the reaction mixture to separate the composite pigment;   washing the separated composite pigment; and   drying the separated composite pigment.