1991 Volume 39 Issue 7 Pages 1837-1842
An aqueous coating was studied using various water-insoluble polymers. In an aqueous suspension system of micronized polymers, the dissolving temperature (DT) of polymers dispersed in a plasticizer upon steady heating, and the cloud point (CP) of the resultant polymer solutions upon steady cooling was examined. The plasticizers with low DT and CP showed good compatibility with the polymers. The casting films obtained from various polymer suspensions showed intrinsic dissolution behavior in pH 1.2 to 7.5 aqueous media depending on the type of polymer uesd. Tables coated with the aqueous suspension system showed the same dissolution profiles as those with an organic solution coating. A comparative study of the aqueous suspension and latex dispersion of ethylcellulose showed that the latex system needed less plasticizer for film formation than the aqueous suspension system. Tablet coating and granule coating were performed using the aqueous suspension system of a jet mill ground acid-alkaline soluble polymer with propylene glycol and the latex dispersion system of an enteric anionic methacrylate with polyethylene glycol 6000, respectively. The results indicate that propylene glycol can act as a temporary plasticizer which mostly evaporates during the coating process, and that water as well as the plasticizer plays an important role in the film formation of the latex particles.
