GB911483A - Encapsulated emulsions and processes for their preparation - Google Patents

Abstract

Microcapsules composed of a gellable hydrophilic colloid enclosing a water-in-oil emulsion containing an "anti-inversion agent" in the oil phase and prepared by a coacervation process (see Group VI) comprise the dye D and C Green No. 5 dissolved in the aqueous phase of the emulsion. Suitable colloids are gelatin, agar, casein, albumin, pectins, starch and fibrinogen and the anti-inversion agent may be non-ionic surfactant, hydrogenated castor oil, a solid fat, a sterol or a natural or synthetic wax. Specification 751,600 is referred to.ALSO:Microcapsules for use in fertilizers as a source of nitrogen consist of an aqueous urea-in-oil emulsion contained within a mantle of a gellable hydrophilic colloid, e.g. gelatin, agar, albumen, casein, pectins, starch or fibrinogen, the oil phase of the emulsion (e.g. corn oil) containing an "anti-inversion agent", e.g. hydrogenated castor oil or a solid fat, sterol or natural or synthetic wax or a non-ionic surfactant. They are produced by a concervation process whereby the colloid is caused to deposit from an aqueous roll thereof on to emulsion particles suspended therein the capsule walls subsequently being gelled and hardened (see Group VI). Specification 751,600 is referred to.ALSO:Particles of a hydrophilic liquid-in-oil emulsion are encapsulated by a process wherein the said emulsion containing an anti-inversion agent in the oil phase is dispersed in a coacervating solution comprising a coacervating agent and an aqueous sol of a coacervating colloid at a temperature above the gel point of the said colloid to form a secondary emulsion upon which the coacervate is deposited and which may subsequently be gelled and hardened by cooling and treatment with a hardener or plasticizer e.g. aqueous formaldehyde. A conventional thickening agent e.g. acacia, tragacanth, methyl- or carboxymethyl-cellulose, magnesium aluminium silicate, polyglycols, glycerin or syrups may be added to both the internal hydrophilic liquid phase and to the coacervating solution, and conventional emulsifying agents may be used in the preparation of the primary emulsion. The anti-inversion agent may be any which is capable of preventing the inversion of the primary emulsion on its dispersion in the coacervating solution e.g. surface active agents (preferably non-ionic) e.g. sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters and oil thickening agents e.g. natural and synthetic waxes, solid fats, sterols and ethyl cellulose. Suitable coacervating colloids are gelable hydrophilic colloids e.g. gelatin (preferred), agar-agar, alginates, casein, pectins, starch and fibrinogen. The coacervating agent may be an electrolyte e.g. a salt having an alkali or alkali metal cation and an organic or inorganic anion or a water soluble solvent in which the coacervating colloid is less soluble than it is in water. The primary emulsion particles may contain additional materials dissolved or suspended in either or both phases, e.g. pharmaceuticals, vitamins, cosmetic ingredients, fertilizers, plant growth hormones, fungicides, bactericides, viricides and pesticides. Specific examples relate inter alia to encapsulated emulsions comprising: (a) urea in an internal aqueous phase (fertilizer preparation); (b) cod liver oil (oil phase) and ascorbic acid (aqueous phase) for incorporation into dry cereals; (c) neomycin (aqueous phase) for incorporation into ointments; (d) an ethanolic solution of ethylene dibromide in peanut oil (nematocidal preparation). Reference is also made to orally and parenterally administrable pharmaceutical forms which may have sustained release characteristics. Detailed examples of the preparation of the capsules are given. Specification 751,600 is referred to.