Core-shell composite inorganic pigments and method of preparation for crystallizable glass frit compositions
Aqueous chemical routes and finished compositions of a core-shell particulate material for application in crystallizable glass enamel are disclosed. A composition of particles containing a shell of inorganic oxides or mixed-metal inorganic oxides and a core material of complex inorganic colored pigment, wherein the shell material is comprised of any single oxide or combination of oxides is taught. Preferred elements of composition for the shell are oxides and silicates of Ti, Ni, Zn, Al, Zr, Si, Sn, Bi, Na, K, and B. Core materials may be any material commonly classified as a complex inorganic colored pigment. The resulting particles function in glass enamel formulations as coloring agents and additives for partial crystallization of the glass material, and provide modification of glass melt temperature, durability, acid resistance, and other desirable properties.
1. A core-shell composite material comprising an inorganic pigment core particle and a shell of a metal oxide material, wherein said shell completely surrounds said inorganic pigment core particle, and wherein the inorganic pigment is a complex inorganic colored pigment (CICP).
2. The core-shell material according to claim 1 wherein the shell is selected from a single layer, mixed layer materials, and multiple layer materials, said layer comprising a metal oxide selected from oxides of Zn, Al, Zr, Si, Sn, Bi, Na, K, B, and mixtures thereof.
3. The core-shell material according to claim 2 wherein the core particle has a diameter of from about 0.05 μm to about 5.0 μm.
4. The core-shell material according to claim 3 wherein the core particle has a diameter of from about 0.3 μm to about 2 μm.
5. The material according to claim 3 wherein the shell has a thickness of from about 1 nm to about 600 nm.
6. The core-shell material according to claim 1 wherein the shell material is from about 0.2% to about 50% by weight of the core-shell material.
7. The core-shell material according to claim 6 wherein the shell material is from about 3% to about 18% by weight of the core-shell material.
8. The core-shell material according to claim 1 wherein the shell is a layered material in crystalline form.
9. The core-shell material according to claim 1 wherein the shell is a layered material in amorphous form.
10. The core-shell material according to claim 1 wherein the shell material contains up to about 50% of a second material comprising a second metal oxide selected from oxides of Ti, Ni, Zn, Al, Zr, Si, Sn, Bi, Na, K, B, and mixtures thereof.
11. An enamel composition comprising from about 0.2% to about 35% of the core-shell material of claim 1 together with from about 40% to about 80% by weight of glass frit.
12. The enamel composition according to claim 11 which includes an organic vehicle.
13. The core-shell material according to claim 1 wherein the shell material is selected from Bi 2 SiO 5 , Ni 2 SiO 4 , Zn 2 SiO 4 , and mixtures thereof.
14. The core-shell material according to claim 1 wherein the core comprises a copper chrome oxide spinel particle, and shell of single metal oxides selected from SnO 2 , ZnO, and SiO x , wherein x is any number commonly designated in the class of amorphous silicas.
15. The core-shell material according to claim 1 wherein the shell precipitated onto the core from an aqueous solution of metal salts selected from Ti, Ni, Al, Zr, Zn, Si, Sn, Bi, Na, K, Li and B metal salts.
16. The core-shell material according to claim 15 wherein the precipitate is the result of manipulation of the pH of the solution.