Encapsulated emulsions and processes for their preparation

Abstract

Abstract Particles of a (primary) oil-in-hydrophilic liquid emulsion containing a thickening agent in the hydrophilic liquid phase are encapsulated by forming a secondary emulsion comprising the said primary emulsion dispersed in a coacervating medium comprising an aqueous dispersion of at least two coacervating polymers, at least one of which is a hydrophilic colloid and at least one of which is a linear macromolecular synthetic polymer and causing the polymers to coacervate and thus coat the dispersed primary emulsion particles by altering the pH or by dilution with water. Suitable thickening agents are: acacia, tragacanth, methyl- and carboxymethyl-cellulose, magnesium aluminium silicate, polyglycols, glycerin and syrups. As hydrophilic colloids there are mentioned gelable and nongelable hydrophilic colloids e.g. gelatine, agar, albumen, alginates, deacetylated chitin, acacia, starch and fibrinogen. Suitable polymers are those whose structure comprises both lipophilic and hydrophilic units, e.g. styrene-maleic acid amide and methyl-vinyl ether-maleic acid copolymers, polymethacrylic acid, carbohydrate acetate phthalates and (preferably) hydrolysed styrene-maleic anhydride copolymers and modifications thereof, in particular those of general formula [-R-R1-]n, wherein R represents lipophilic polymer units of which more than 70% are styrene residues and R1 represents hydrophilic units of which more than 50% are maleic acid residues. Solubilizing agents may be added to increase the concentration of polymer, e.g. solvents and polysaccharides, e.g. alginates, pectins, methyl- and carboxymethyl-cellulose and Irish moss derivatives. Either or both phases of the primary emulsion may contain dissolved or suspended "active" ingredients which render the product of the invention useful as sustained release fertilizers, plant growth regulants, bactericides, and pesticides, as food additives, cosmetic ingredients and medicines. Specific examples include: (a) mineral oil-in-caffeine aqueous suspension in gelatine and styrene-maleic acid copolymer, and (b) corn oil-in-aqueous rotenone suspension in fibrinogen and cellulose acetate phthalate. Specification 751,600 is referred to.

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