Process and apparatus for producing inorganic spheres

1. A process for producing inorganic spheres, which comprises injecting an aqueous liquid containing an inorganic compound comprising sodium silicate or potassium silicate into a laminar flow of an organic liquid which runs at a flow rate of from 0.001 to 2 m/s in a flow path compartmentalized by a partition wall through a plurality of inlet holes formed in one partition wall to form a W/O type emulsion containing the organic liquid as a dispersion medium and the aqueous liquid containing the inorganic compound as a dispersed phase, and solidifying the aqueous liquid containing an inorganic compound in the W/O type emulsion, wherein the partition wall having a plurality of inlet holes is made of a metal sheet having a surface subjected to water repellent treatment which is carried out using a solvent-soluble thermoplastic fluororesin, and wherein said laminar flow of the organic liquid is at a Reynolds number of at most 2,100.

2. The process for producing inorganic spheres according to claim 1 , wherein the thickness of the metal sheet is from 10 to 500 μm.

3. The process for producing inorganic spheres according to claim 1 , wherein the thickness of the metal sheet is from 30 to 200 μm.

4. The process for producing inorganic spheres according to claim 1 , wherein the metal sheet is made from a material selected from the group consisting of nickel, a nickel alloy and stainless steel.

5. The process for producing inorganic spheres according to claim 1 , wherein the metal sheet is made from stainless steel.

6. The process for producing inorganic spheres according to claim 1 , wherein the water repellent treatment is carried out by spraying or spreading.

7. The process for producing inorganic spheres according to claim 1 , wherein the water repellent treatment gives a water repellent coating having a thickness of from 0.001 to 5 μm.

8. The process for producing inorganic spheres according to claim 1 , wherein the inlet holes are formed in a number of at least 100.

9. The process for producing inorganic spheres according to claim 1 , wherein the inlet holes are formed in a number of at least 1000.

10. The process for producing inorganic spheres according to claim 1 , wherein the ratio of the linear velocity of the organic liquid in the flow direction to the linear velocity of the aqueous liquid in the flow direction is from 1 to 500.

11. The process for producing inorganic spheres according to claim 1 , wherein the ratio of the linear velocity of the organic liquid in the flow direction to the linear velocity of the aqueous liquid in the flow direction is from 10 to 300.

12. The process for producing inorganic spheres according to claim 1 , wherein the W/O type emulsion is solidified by adding an acid.

13. The process for producing inorganic spheres according to claim 1 , wherein the organic liquid is a C 9-12 saturated hydrocarbon.

14. The process for producing inorganic spheres according to claim 1 , wherein the Reynolds number of the organic liquid is at most 500.

15. The process for producing inorganic spheres according to claim 1 , wherein the cross sections of the inlet holes have at least one shape selected from the group consisting of circular, rectangular, triangular and elliptic shapes.

16. The process for producing inorganic spheres according to claim 1 , wherein the quadruple of the hydraulic radii r of the cross sections of the inlet holes are from 0.1 to 100 μm.

17. The process for producing inorganic spheres according to claim 1 , wherein the quadruple of the hydraulic radii r of the cross sections of the inlet holes are from 1 to 80 μm.

18. The process for producing inorganic spheres according to claim 1 , wherein the fluororesin is a perfluoropolymer.