Method of manufacturing minute capsules

摘要

In a process for the production of coated capsules by coacervation, the core material and a coacervate solution of the wall-forming polymer are dispersed as minute entities in an agitated liquid vehicle, the solubility of the wall-forming polymer decreasing with increasing temperature, and the system is heated above the gel point of the wall-forming polymer to harden the walls deposited about the entities of core material. In order to produce phase separation to effect an emergence of a coacervate phase of the wall-forming polymer a complementary polymer may be added to the system. Separation of the capsules from the liquid vehicle is carried out at the elevated temperature, unless agents are added to the system to accelerate the hardening process, in which case separation can be carried out after recooling. In the one form a coacervate solution of the wall-forming polymer is formed separately from the liquid vehicle in which it is insoluble, and the system is made up by combining the component phases and agitating and heating as required. Incomplete systems, lacking one or more component, may be stored for future use. In cases where the liquid vehicle is used as the solvent for the wall-forming polymer coacervation may be induced by, in conjunction with the property of decreasing solubility at elevated temperature, changing conditions such as microion concentration. Examples of wall-forming polymers having the requisite solubility properties are methyl cellulose, polyvinylmethyl ether, and ethylhydroxyethyl cellulose. Suitable complementary polymers to assist in formation of a coacervate solution of methyl cellulose include dextran, hydroxypropyldextran, polyvinyl alcohol or polyvinylpyrrolidone. The method is particularly suited to the coating of core materials which are insoluble in the liquid vehicle, including chloroform, chlorinated biphenyl, kerosene, acetylated monoglyceride, lemon oil, menthol, aspirin, resins, pigments and dies. In particular examples described, aqueous dextran solution is used to facilitate coacervation of methyl cellulose aqueous wall-forming solution when various materials are coated, agitation and heating to 50-60 DEG C. producing the required particle size and encapsulation. An example of a wall-hardening agent is a mixture of aqueous sorbitol solution; mono-and di-glycerides of fat forming fatty acids, and an aqueous solution of tannic acid.ALSO:In a process for the production of coated capsules of, for example, aspirin, by coacervation, the core material and a coacervate solution of the wall-forming polymer are dispersed as minute entities in an agitated liquid vehicle, the solubility of the wall-forming polymer decreasing with increasing temperature, and the system is heated above the gel point of the wall-forming polymer to harden the walls deposited about the entities of core material. In order to produce phase separation to effect an emergence of a coacervate phase of the wall-forming polymer a complementary polymer may be added to the system. Separation of the capsules from the liquid vehicle is carried out at the elevated temperature, unless agents are added to the system to accelerate the hardening process, in which case separation can be carried out after recooling. In the one form a coacervate solution of the wall-forming polymer is formed separately from the liquid vehicle in which it is insoluble, and the system is made up by combining the component phases and agitating and heating as required. Incomplete systems, lacking one or more component, may be stored for future use. In cases where the liquid vehicle is used as the solvent for the wall-forming polymer coacervation may be induced by, in conjunction with the property of decreasing solubility at elevated temperature, changing conditions such as microion concentration. Examples of wallforming polymers having the requisite solubility properties are methyl cellulose, polyvinylmethyl ether, and ethylhydroxyethyl cellulose. Suitable complementary polymers to assist in formation of a coacervate solution of methyl cellulose include dextran, hydroxypropyldextran, polyvinyl alcohol or polyvinylpyrrolidone. The method is particularly suited to the coating of core materials which are insoluble in the liquid vehicle.