GB929470A - Encapsulated emulsions and processes for their preparation - Google Patents

Abstract

Particles of a (primary) hydrophilic liquid-in-oil emulsion containing an anti-inversion agents in the oil phase are encapsulated by dispersing the said primary emulsion in an aqueous dispersion of a linear macromolecular synthetic polymer and a coacervating agent to form a secondary emulsion upon which the polymer is deposited and may subsequently be gelled and hardened. The primary emulsion may contain a conventional emulsifying and/or thickening agent, examples of the former being: esters of polyhydric alcohols, sorbitan and polyoxyethylene derivatives and of the latter (which may also be present in the coacervation solution); acacia, tragacanth, methyl- and carboxymethyl-cellulose, magnesium aluminium silicate, polyglycols, glycerine and syrups. The anti-inversion agent may be any material capable of preventing the inversion of the primary emulsion on dispersion thereof in the coacervating solution, examples being: surface active agents (preferably non-ionic), oil thickening agents, e.g. waxes, fats, sterols and conventional oil-gelling or oil-thickening agents. Suitable polymers are those of substantially linear structure which comprises both lipophilic units, e.g. styrene, substituted styrene, ether- or ester-substituted ethylene residues and hydrophilic units, e.g. maleic, acrylic, crotonic acid, maleic acid or acrylic acid amide residues, examples of such polymers being: hydrolysed styrene-maleic anhydride copolymers (preferred), styrene-maleic acid amide copolymers, sulphonated polystyrenes, methylvinyl ether-maleic acid copolymer and carbohydrate acetate phthalates. Solubilizing agents for such polymers, especially galactose polysaccharides such as Irish moss derivates may be used to obtain polymer solutions of suitable concentration. As coacervating agents there are mentioned aqueous solutions of electrolytes, and water-soluble liquids in which the polymers are less soluble than in water and these may be added to the polymer solution before or after the formation of the secondary emulsion. The primary emulsion may contain dissolved or suspended materials which render the capsules of the invention useful, e.g. as sustained release fertilizers, plant growth regulants, bactericides, pesticides, fungicides, food additives, vitamin preparations, cosmetic ingredients and pharmaceuticals. Specific examples include an aqueous urea solution-in-corn oil emulsion coated with styrene - maleic acid copolymer which is useful as a slow-release fertilizer. Specification 751,600 is referred to.