Mechanical Particle Coating Using Polymethacrylate Nanoparticle Agglomerates for the Preparation of Controlled Release Fine Particles
We aimed to understand the factors controlling mechanical particle coating using polymethacrylate. The relationship between coating performance and the characteristics of polymethacrylate powders
was investigated. First, theophylline crystals were treated using a mechanical powder processor to obtain theophylline spheres (<100 μm). Second, five polymethacrylate latexes were
powdered by spray freeze drying to produce colloidal agglomerates. Finally, mechanical particle coating was performed by mixing theophylline spheres and polymethacrylate agglomerates using the
processor. The agglomerates were broken under mechanical stress to coat the spheres effectively. The coating performance of polymethacrylate agglomerates tended to increase as their pulverization
progressed. Differences in the grindability of the agglomerates were attributed to differences in particle structure, resulting from consolidation between colloidal particles. High-grindability
agglomerates exhibited higher pulverization as their glass transition temperature (Tg) increased and the further pulverization promoted coating.
We therefore conclude that the minimization of polymethacrylate powder by pulverization is an important factor in mechanical particle coating using polymethacrylate with low deformability.
Meanwhile, when product temperature during coating approaches Tg of polymer, polymethacrylate was soften to show high coating performance by plastic deformation. The effective coating by
this mechanism may be accomplished by adjusting the temperature in the processor to the Tg.