Method for manufacturing microcapsules

1. A process for producing microcapsules, said process comprising (1) and (2):

(1) emulsifying an organic phase comprising at least one organic compound and a tetraalkoxysilane such that a content of the tetraalkoxysilane in the organic phase is not less than 10% by mass and not more than 60% by mass on the basis of the organic compound, in a water phase comprising a surfactant, and subjecting the resulting emulsion to a sol-gel reaction under acidic conditions to form microcapsules each comprising a core and a first shell comprising silica and encapsulating the core; and

(2) further adding a tetraalkoxysilane to a water dispersion comprising the microcapsules obtained in (1), and subjecting the obtained mixture to a sol-gel reaction while maintaining an initial pH value in the sol-gel reaction in (2) below an initial pH value in the sol-gel reaction in (1), thereby forming the microcapsules comprising a second shell comprising silica and encapsulating the first shell.

2. The process for producing microcapsules according to claim 1 , further comprising (3):

(3) mixing a dispersion comprising the microcapsules obtained in (2) with an aqueous solution of an organic polymeric compound to form microcapsules comprising a third shell.

3. The process for producing microcapsules according to claim 1 , wherein the tetraalkoxysilane is added dropwise during (2), and a time of the dropwise addition of the tetraalkoxysilane is not less than 10 min and not more than 1,000 min.

4. The process for producing microcapsules according to claim 1 , wherein an amount of the tetraalkoxysilane added during (1) is not less than 10% by mass and not more than 40% by mass on the basis of the organic compound.

5. The process for producing microcapsules according to claim 1 , wherein an amount of the tetraalkoxysilane added during (2) is not less than 10% by mass and not more than 40% by mass on the basis of the organic compound.

6. The process for producing microcapsules according to claim 1 , wherein the initial pH value in the sol-gel reaction in (1) is not less than 3.5 and not more than 4.3.

7. The process for producing microcapsules according to claim 1 , wherein the initial pH value in the sol-gel reaction in (2) is not less than 2.5 and less than 3.5.

8. The process for producing microcapsules according to claim 1 , wherein the organic compound present in the core is at least one material selected from the group consisting of a fragrance material, a fragrance precursor, an oil, an antioxidant and a solvent.

9. The process for producing microcapsules according to claim 2 , wherein the organic polymeric compound is at least one compound selected from the group consisting of a water-soluble synthetic polymer compound and a natural polymer compound.

10. The process for producing microcapsules according to claim 1 , further comprising (1-1):

(1-1) adding a cationic polymeric compound to the water dispersion comprising the microcapsules obtained from (1) prior to (2).

11. The process for producing microcapsules according to claim 1 , wherein the organic compound present in the core is the fragrance precursor.

12. The process for producing microcapsules according to claim 11 , wherein the fragrance precursor is a silicic acid ester comprising an alkoxy component derived from a fragrance alcohol.

13. Microcapsules each comprising a core comprising at least one organic compound, a first shell encapsulating the core, and a second shell encapsulating the first shell,

wherein the first shell encapsulating the core comprises silica and has a thickness of not less than 5 nm and not more than 20 nm;

wherein the second shell encapsulating the first shell comprises silica and has a thickness of not less than 10 nm and not more than 100 nm;

wherein the ClogP value of the at least one organic compound in the core is not less than 2; and

wherein the microcapsules have an average particle size of not less than 0.5 μm and not more than 50 μm.

14. The microcapsules according to claim 13 , further comprising a third shell present on and in contact with the second shell, said third shell comprising an organic polymeric compound.

15. Microcapsules produced by the process according to claim 1 , comprising a core comprising

at least one organic compound,

a first shell encapsulating the core and comprising silica, and

a second shell encapsulating the first shell and comprising silica, the second shell having a mesoporous structure with a pore size of more than 2 nm and not more than 50 nm,

wherein the microcapsules have an average particle size of not less than 0.5 μm and not more than 50 μm.

16. The process for producing microcapsules according to claim 1 , wherein a total amount of the tetraalkoxysilane added present during the process is not less than 20% by mass and not more than 60% by mass on the basis of the organic compound.

17. The process for producing microcapsules according to claim 1 , wherein the surfactant present during (1) is a cationic surfactant.

18. The process for producing microcapsules according to claim 10 , wherein an equivalent amount of a cationic group in the cationic polymeric compound is not less than 1 meq/g and not more than 10 meq/g.

19. The process for producing microcapsules according to claim 10 , wherein an amount of the cationic polymer compound added is not less than 0.05% by mass and not more than 5% by mass, based on a total amount of the organic compound in the microcapsules.