| 摘要 |
Minute capsules each having a solid or liquid nucleus enclosed by a seamless, rigid wall of hydrophobic, film-forming, polymeric material are prepared by establishing a system comprising a liquid vehicle constituting over 70% of the system and comprising a solvent for the polymeric material and a phase-separation-inducing solute and dispersed therein, particles of the nucleus material and the polymeric wall-forming material, the solvent being chosen so that the polymer is soluble therein at elevated temperatures and insoluble at a lower temperature. The system is heated with agitation to a temperature at which the polymer dissolves, whereupon, the phase-separation-inducing solute causes a separate liquid phase of polymer and solvent to be formed which has a viscosity between 100 and 10,000 centipoises and which deposits on the core material particles. Thereafter, the system is cooled with continued agitation to a temperature at which the liquid capsule walls give up the solvent to give the finished capsules which may be separated, washed and dried. Examples relate to the encapsulation of aspirin in ethyl cellulolose using cyclohexane as solvent and butyl rubber as phase-separation-inducing solute (optionally, acetic anhydride may be present to clear potentially toxic materials, e.g. salicylic and acetic acids, from the aspirin) and the same system using an aromatic-type petroleum solvent; reference is also made to the encapsulation of ammonium dichromate, acetyl p-amino phenol, amphetamine sulphate, aluminium aspirin, sodium bicarbonate, gelatin, cellulose acetate hydrogen phthalate, polyvinyl pyrrolidone, mannitol, glyceryl guiacolate, dextro-methorphan hydrobromide, calcium gluconate and carboxymethyl cellulose. Other coating polymers mentioned are ethyl hydroxy ethyl cellulose, polyvinyl pyrrolidone/vinyl acetate and vinyl chloride/vinyl acetate copolymers, other solvents are n-hexane plasticized with monoacetylated glyceride, ligroin, methyl cyclohexane, toluene/cyclohexane, benzene and toluene. Polybutadiene is mentioned as an alternative phase-separation-inducing solute.ALSO:Microcapsules each having a solid or liquid nucleus enclosed by a seamless, rigid wall of hydrophobic, film-forming, polymeric material may contain as nucleus material a medicament, those specified being acetyl-p-aminophenol, amphetamine sulphate, aluminium aspirin, sodium bicarbonate, glyceyl guiacolate, calcium gluconate and dextromethorphan hydrobromide. Specified film-forming materials are ethyl cellulose, ethyl hydroxyethyl cellulose, polyvinyl pyrrolidone/vinyl acetate and vinyl chloride/vinyl acetate copolymers. |
