LATICES OF CELLULOSIC POLYMERS; MANUFACTURE, CHARACTERIZATION AND APPLICATION AS PHARMACEUTICAL FILM COATINGS
Abstract
An investigation was undertaken to study the feasibility of producing aqueous colloidal dispersions, or pseudo latices, of F.D.A. approved cellulosic polymers, which would provide a base for the design of a new totally aqueous film coating system, as an alternative to the traditional film coating systems based in organic solvent solutions of polymers. The latex systems permitted the incorporation of a high concentration of coating solids, while possessing a moderate viscosity for a fast coating system, requiring less heat for drying than the aqueous solutions of polymers. Latices of ethyl cellulose and cellulose acetate phthalate were prepared following a microemulsification technique. An organic solvent solution of the polymer was emulsified in a continuous aqueous phase in the presence of emulsifiers, with the size of the emulsions droplets being further reduced by sonification and/or homogenization. The subsequent removal of the organic solvent by vacuum distillation produced a latex of very small particle size and narrow size distribution. The latices so prepared were characterized by very low viscosities at concentrations of solids as high as 44%, which exhibited non-Newtonian dilatant flow. An ethyl cellulose latex plasticized with triacetin, propylene glycol or glycerin produced a brittle, transparent or nearly transparent film. Combinations of the ethyl cellulose latex with water soluble polymers, specifically methyl cellulose and hydroxypropyl methyl cellulose, in a plasticized system, produced the desired strength and flexibility for pharmaceutical film coatings. A study of the permanence of the plasticizers in free films showed that propylene glycol was lost from the films, with time, following a first order kinetic process with a rate constant of 0.014 days('-1), in latex based films, and 0.009 days('-1) from organic solvent solution cast films. Triacetin was found to be permanent in latex based free films over a period of three months. A selection of combinations of ethyl cellulose latex and hydroxypropyl methyl cellulose 15 cps, containing approximately 30% solids, plasticized with a mixture of triacetin and glycerine / or triacetin and propylene glycol, were applied onto tablets by a fluid bed spray film coating technique. Combinations containing glycerin as a component of the plasticizer system, with and without pigments, produced a satisfactory film coating in a short period of time. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI
Degree
Ph.D.
Subject Area
Pharmacology
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