Composite particles containing an active substance

A process of use in the preparation of composite particles comprising at least

• one core comprising at least one organic polymer in which is dispersed at least one hydrophobic, active material, wherein the hydrophobic active material is a cosmetic, pharmaceutical, food or plant-protection material,
• one external coating comprising at least one oxide and/or hydroxide of aluminum, of silicon, of zirconium and/or of a transition metal and
• one intermediate layer, present at least partially between the core and the external coating and comprising at least one alkaline earth metal hydroxide and comprising at least:
• the incorporation of at least one hydrophobic active material in particles based on at least one organic polymer, said particles being in aqueous, alcoholic or aqueous/alcoholic dispersion and, optionally formed in conjunction with the incorporation of said active material,
• the dissolution of at least one alkaline earth metal salt in the liquid phase of the dispersion of polymer particles, which particles comprise at least one hydrophobic active material and are obtained according to the preceding stage,
• the addition of a base in a sufficient amount to precipitate a layer of oxide or of hydroxide of said alkaline earth metal at the surface of said particles,
• the bringing of at least one water-soluble silicon, aluminum, zirconium and/or transition metal salt into contact, in the liquid phase of the particle dispersion obtained on conclusion of the preceding stage, with at least one agent capable of reacting with said soluble salt to form a precipitate composed of the corresponding oxide or hydroxide at the surface of said particles and,
• the drying and the recovery of the composite particles thus obtained.