GB929408A - Encapsulated emulsions and processes for their preparation - Google Patents

Abstract

Particles of a (primary) hydrophilic liquid-in-oil emulsion containing an anti-inversion agent in the oil phase are encapsulated by dispersing the said primary emulsion to form a secondary emulsion in an aqueous dispersion of at least two coacervating colloids at least one of which is a hydrophilic colloid and at least one of which is a linear macromolecular synthetic polymer and causing a coacervate of the polymers to deposit about the particles of the primary emulsion and, if desired, subsequently drying and/or hardening the capsules. The primary emulsion may contain conventional emulsifying agents e.g. esters of polyhydric alcohols, sorbitan derivatives, and sorbitan polyoxyethylene derivatives and advantageously contains a thickening agent, e.g. acacia, methyl cellulose, magnesium aluminium silicate, glycium and syrups in the hydrophilic liquid phase. As anti-inversion agents there are mentioned surface-active agents (preferably non-ionic), and conventional oil-gelling and oil-thickening agents, e.g. waxes, solid fats and sterols. Suitable hydrophilic colloids are naturally occurring gelable and nongelable hydrophilic colloids and derivatives thereof, e.g. gelatine, agar, albumen, deacetylated chitins, pectins, acacia, starch and fibrinogen. Suitable linear macromolecular synthetic polymers are those whose structure comprises both lipophilic units and hydrophilic units, e.g. styrene-maleic amide copolymers, sulphonated polystyrenes, carbohydrate acetate phthalates and (preferably) hydrolysed styrenemaleic anhydride copolymers of general formula [-R-R1-]n, wherein R represents lipophilic units of which more than 70% are styrene residues and R1 represents hydrophilic units of which more than 50% are maleic acid residues. Coacervation may be induced by alteration of the pH of the polymer dispersion or by dilution thereof with water. Either or both phases of the primary emulsion may contain dissolved or suspended "active" ingredients which render the encapsulated products useful, e.g. as sustained release fertilizers, plant growth regulants, pesticides, bactericides, food additives, cosmetic ingredients, vitamin preparations and pharmaceutical materials. Specific examples include: (a) aqueous chloral hydrate-in-mineral oil emulsion in gelatine and styrene-maleic acid copolymer; (b) glycerine suspension of rotenone in mineral oil in serum albumin and styrene-maleic amide copolymer and (c) aqueous urea solution-in-peanut oil in gelatine and styrene-maleic acid copolymer. Specification 751,600 is referred to.