Process for producing dispersion of hollow fine SiO
View Patent ↗To provide a process for producing a dispersion of hollow fine SiO 2 particles which contains no residual core fine particles, generates no uncontrollable agglomerates, and is easy to filtrate. A process for producing a dispersion of hollow fine SiO 2 particles having hollow fine SiO 2 particles dispersed in a dispersion medium, which comprises at least the following steps (a), (b) and (c): (a) a step of reacting a precursor of SiO 2 at a pH higher than 8 in the presence of fine ZnO particles constituting the core in the dispersion medium to form SiO 2 , thereby to obtain a dispersion of fine particles comprising the fine ZnO particles covered with the formed SiO 2 ; (b) a step of mixing an acidic cation exchange resin with the dispersion of fine particles obtained in the above step (a) to bring them into contact with each other, to dissolve the fine ZnO particles as the core at a pH within a range of from 2 to 8; and (c) a step of separating the acidic cation exchange resin by solid-liquid separation after the fine ZnO particles are completely dissolved, to obtain the dispersion of hollow fine SiO 2 particles.
1. A process for producing a dispersion of hollow fine SiO 2 particles in a dispersion medium, comprising:
reacting a precursor of SiO 2 at a pH higher than 8 in the presence of fine ZnO particles in a dispersion medium such that a dispersion of fine particles comprising the fine ZnO particles covered with SiO 2 is obtained;
dissolving the fine ZnO particles with an acidic cation exchange resin by adding the acidic cation exchange resin to the dispersion of fine particles in an amount which makes a total exchange capacity of the acidic cation exchange resin within a range of from 1.1 to 5 times an amount of zinc ions generated in the dispersion of fine particles, adjusts the pH to within a range of from 2 to 8, and adsorbs the zinc ions; and
separating the acidic cation exchange resin by solid-liquid separation after the fine ZnO particles are dissolved such that the dispersion of hollow fine SiO 2 particles is obtained without separation of the zinc ions by ultrafiltration.
2. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 1 , wherein the acidic cation exchange resin has —SO 3 H groups.
3. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 1 , wherein the pH at which the fine ZnO particles are dissolved to zinc ions is from 2 to 6.
4. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 1 , wherein the acidic cation exchange resin is a porous type.
5. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 1 , wherein a mesh size of the acidic cation exchange resin is from 10 to 50.
6. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 1 , wherein the fine ZnO particles are dissolved at a temperature of from 10 to 100° C.
7. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 1 , wherein the thickness of the shell of the hollow fine SiO 2 particles is within a range of from 1 to 20 nm and is from one-fifth to one-third of the average primary particle size of the fine SiO 2 particles.
8. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 1 , wherein the average primary particle size of the fine ZnO particles is from 5 to 200 nm and the average primary particle size of the hollow fine SiO 2 particles is from 5 to 200 nm.
9. A process for producing a dispersion of hollow fine SiO 2 particles in a dispersion medium, comprising:
reacting a precursor of SiO 2 at a pH higher than 8 in the presence of fine ZnO particles in a dispersion medium such that a dispersion of fine particles comprising the fine ZnO particles covered with SiO 2 is obtained;
dissolving the fine ZnO particles with an acidic cation exchange resin by adding the acidic cation exchange resin to the dispersion of fine particles in an amount which adjusts the pH to within a range of from 2 to 8, adsorbs the zinc ions generated in the dispersion, and keeps an average agglomerated particle size of agglomerated particles in the dispersion of the hollow fine SiO 2 particles to within a range of from 60 to 400 nm; and
separating the acidic cation exchange resin by solid-liquid separation after the fine ZnO particles are dissolved such that the dispersion of hollow fine SiO 2 particles is obtained without separation of the zinc ions by ultrafiltration.
10. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 9 , wherein the acidic cation exchange resin has —SO 3 H groups.
11. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 9 , wherein the precursor of SiO 2 is an alkoxysilane or a hydrolysate of the alkoxysilane, and wherein the dispersion medium is a solvent mixture of water and organic solvent, and the water is present in the solvent mixture in an amount of at least 5 mass %.
12. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 9 , wherein the pH at which the fine ZnO particles are dissolved to zinc ions is from 2 to 6.
13. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 9 , wherein the acidic cation exchange resin is a porous type.
14. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 9 , wherein a mesh size of the acidic cation exchange resin is from 10 to 50.
15. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 9 , wherein the fine ZnO particles are dissolved at a temperature of from 10 to 100° C.
16. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 9 , wherein the thickness of the shell of the hollow fine SiO 2 particles is within a range of from 1 to 20 nm and is from one-fifth to one-third of the average primary particle size of the fine SiO 2 particles.
17. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 9 , wherein the average primary particle size of the fine ZnO particles is from 5 to 200 nm and the average primary particle size of the hollow fine SiO 2 particles is from 5 to 200 nm.
18. A process for producing a dispersion of hollow fine SiO 2 particles in a dispersion medium, comprising:
reacting a precursor of SiO 2 at a pH higher than 8 in the presence of fine ZnO particles in a dispersion medium such that a dispersion of fine particles comprising the fine ZnO particles covered with SiO 2 is obtained;
adjusting the pH of the dispersion to within a range of from 2 to 8 by adding an acidic cation exchange resin to the dispersion of fine particles in an amount which dissolves the fine ZnO particles without addition of an acid and adsorbs zinc ions generated in the dispersion of fine particles; and
separating the acidic cation exchange resin by solid-liquid separation after the fine ZnO particles are dissolved such that the dispersion of hollow fine SiO 2 particles is obtained without separation of the zinc ions by ultrafiltration.
19. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 18 , wherein the acidic cation exchange resin has —SO 3 H groups.
20. The process for producing a dispersion of hollow fine SiO 2 particles according to claim 18 , wherein the acidic cation exchange resin is a porous type.