| 摘要 |
Finely divided lipophilic material is encapsulated by a process wherein there are brought together in the presence of the dispersed lipophilic material, aqueous solutions of an electrophoretically chargeable styrene-maleic acid copolymer and of an oppositely chargeable gelable colloid at a temperature above the gelation temperature of the colloid and at a pH at which the copolymer is electrophoretically charged and the colloid is oppositely (and preferably equally) charged and at which significant liquid-liquid phase separation of both the polymer and colloid occurs, thereby inducing encapsulation of the lipophilic material within a mantle of copolymer and colloid which may be set by cooling the mixture below the gelation temperature of the colloid. Alternatively, the pH of the mixture may initially be outside the above-mentioned range and is subsequently brought within it and/or setting may be induced by the addition of a highly active carbonyl compound, e.g. formaldehyde, glyoxal, malonic acid dialdehyde, pyruvaldehyde, glyceraldehyde, diacetyl or methyl phenyl ketone or ferric chloride and tannic acid. Specified gelable colloids are gelatin, albumin, casein, deacetylated chitins, polyvinylpyrrolidone, styrene-polyvinylpyridine copolymer, triethanolamine-phthalic acid copolymer, polyamino acids, e.g. polylysine, polyornithine. The styrene-maleic acid copolymers may be represented by the formula (-R-R1-)n wherein R represents lipophilic polymer units of which more than 70% are styrene residues and R1 represents hydrophilic polymer units of which more than 50% are maleic acid residues and the aqueous solutions thereof used in the process may contain organic liquids, e.g. lower alkanols, lower alkylene glycols and lower alkyl triols and solubilizing agents in particular polysaccharides, e.g. alginates, pectins, methyl- and carboxymethyl-cellulose and Irish moss derivatives. The encapsulated product of the invention may be useful, by virtue of the nature of the lipophilic material or of material dissolved therein, as a fertilizer, pesticide, plant growth regulant, food additive (e.g. containing vitamins or fats), medicaments (especially delayed and sustained release oral medicaments), cosmetics and coating compositions useful in the manufacture of record paper, pressure-sensitive tapes and labels and magnetic information storage devices when the lipophilic material contains magnetic or magnetizable particles. A specific example relates to the encapsulation of a Vitamin A oil in styrene-maleic acid copolymer. Specification 751,600 is referred to. |
