Microencapsulation
A process for making microcapsules comprising i) forming a solution of a cross-linker in a liquid; ii) forming a slurry of a surface-modified particulate inorganic material in an aqueous medium; and iii) dispersing the solution of step i) in the slurry of step ii) and causing or allowing the cross-linker to react with the surface-modified particulate inorganic material so as to form a cross-linked microcapsule wall.
1. A process for making microcapsules comprising:
i) forming a solution of a cross-linker in a liquid;
ii) forming a slurry of a surface-modified particulate inorganic material in an aqueous medium; and
iii) dispersing the solution in the slurry and causing or allowing the cross-linker to react with the surface-modified particulate inorganic material so as to form a microcapsule comprising a cross-linked particulate inorganic microcapsule wall,
wherein the surface-modified particulate inorganic material is clay which has been surface-modified with an amino-silane.
2. A process as claimed in claim 1 in which the liquid that is used to form a solution of the cross-linker is substantially insoluble in water.
3. A process as claimed in claim 2 in which the liquid that is used to form a solution of the cross-linker has a solubility in water at 20° C. of less than 10 g/l.
4. A process as claimed in claim 1 in which the liquid that is used to form a solution of the cross-linker further comprises an active material which is an agrochemical.
5. A process as claimed in claim 4 in which the active material is an insecticide.
6. A process as claimed in claim 5 in which the insecticide is a pyrethroid.
7. A process as claimed in claim 6 in which the pyrethroid is lambda-cyhalothrin.
8. A process as claimed in claim 1 in which the particulate inorganic material comprises an oxy-compound of a metal selected from the group consisting of calcium, magnesium, aluminum, silicon, and combinations thereof.
9. A process as claimed in claim 1 in which the particulate inorganic material has a median diameter (d 50 ) less than or equal to 10 μm.
10. A process as claimed in claim 1 in which the particulate inorganic material has a particle size distribution where at least about 90% of the particles by weight are smaller than about 2 μm.
11. A process as claimed in claim 1 in which the particulate inorganic material has a particle size distribution where at least about 90% of the particles by weight are less than about 2 μm and at least about 75% of the particles by weight are less than about 0.25 μm.
12. A process as claimed in claim 1 in which the amino-silane with which the particulate inorganic material has been modified has a chemical structure of X—Y—Z, in which X is a chemical moiety with a high affinity for the particle surface; Z is an amine group and Y is a chemical moiety that links X and Z together.
13. A process as claimed in claim 12 in which X is an alkoxy-silane group.
14. A process as claimed in claim 12 in which Y is a C 2-6 alkylene chain.
15. A process as claimed in claim 1 in which the cross-linker is a polyisocyanate.
16. A process as claimed in claim 1 where the cross-linked microcapsule wall is modified through addition of an extra cross-linking molecule during or after step (iii).
17. A process as claimed in claim 1 in which the particulate inorganic material is natural.
18. A process as claimed in claim 1 in which the particulate inorganic material is synthetic.