method of formation of microcapsules by interfacial cross-linking of resultantes emulsionnant and microcapsules

摘要

1375142 Microcapsules CHAMPION PAPER CO Ltd 20 Feb 1973 [6 March 1972] 8332/73 Heading B8C Oil-containing microcapsules are made by dissolving a non-polymeric polyfunctional isocyanate or an orthoester of a Group IV element in the oil and dispersing it in an aqueous medium containing an hydroxyl group-containing polymeric emulsifying agent and causing the isocyanate or ester to react with the emulsifier to cross-link the latter, thereby producing a polymer which encapsulates the oil droplets. Suitable reactants are: 4,4SP1/SP-diphenylmethane isocyanate, toluene diisocyanate, hexamethylene diisocyanate, triphenylmethane triisocyanate and adducts thereof with polyhydric alcohols, tetraethyl orthosilicate, tetrabutyl titanate and tetrapropyl orthocarbonate. Suitable emulsifiers are polyvinyl alcohol, methyl cellulose and oleophilic starch. Additional hardening may be achieved by treating the resulting microcapsules with a further cross-linking agent, e.g. a formaldehyde condensation product. The oil may contain dissolved or suspended materials which render the product useful as medicines, poisons, foods, cosmetics, adhesives and, particularly, as transfer sheet record materials. The examples relate to products containing such substances, e.g. benzoyl leucomethylene blue and crystal violet lactone, which may be coated on to sheets, e.g. of paper.