Abstract
Fluid dynamics of pellets processed in bottom spray traditional Wurster coating and swirl accelerated air (precision) coating were compared with the intent to understand and facilitate improvements in the coating processes. Fluid dynamics was described by pellet mass flow rate (MFR) obtained using a pellet collection system and images captured using high speed photography. Pellet flow within the partition column was found to be denser and slower in Wurster coating than in precision coating, suggesting a higher tendency of agglomeration during the coating process. The influence of partition gap and load on the MFR indicated that the mechanism of transport of pellets into the coating zone in precision coating depended on a strong suction, whereas in Wurster coating, pellets were transported by a combination of peripheral fluidization, gravity, and weak suction pressure. In precision coating, MFR was found to increase uniformly with air flow rate and atomizing pressure, whereas MFR in Wurster coating did not correlate as well with air flow rate and atomizing pressure. This demonstration showed that transport in precision coating was air dominated. In conclusion, fluid dynamics in precision coating was found to be air dominated and dependent on pressure differential, thus it is more responsive to changes in operational variables than Wurster coating.
Keywords: fluid bed coaters, coating, flow, pellets
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References
- 1.Christensen FN, Bertelson P. Qualitative description of the Wurster-based fluid-bed coating process. Drug Dev Ind Pharm. 1997;23:451–463. doi: 10.3109/03639049709148494. [DOI] [Google Scholar]
- 2.Porter SC, Bruno CH. Coating of pharmaceutical solid-dosage forms. In: Lieberman HA, Lachman L, Schwartz JB, editors. Pharmaceutical Dosage Forms, Tablets. New York NY: Marcel Dekker; 1990. pp. 77–159. [Google Scholar]
- 3.Cole GC. Introduction and overview of pharmaceutical coating. In: Cole GC, editor. Pharmaceutical Coating Technology. London, UK: Taylor & Francis; 1995. pp. 1–5. [Google Scholar]
- 4.Horvath E, Ormos Z. Film coating of dragee seeds by fluidized bed spraying methods. Acta Pharm Tech. 1989;35:90–96. [Google Scholar]
- 5.Wurster DE, inventor. Method of applying coating onto edible tablets or the like. US patent 2 648 609. 1953.
- 6.Jono K, Ichikawa H, Miyamoto M, Fukumori Y. A review of particulate design for pharmaceutical powders and their production by spouted bed coating. Powder Tech. 2000;113:269–277. doi: 10.1016/S0032-5910(00)00310-7. [DOI] [Google Scholar]
- 7.Walter K, inventor. Apparatus for coating solid particles. US patent 5 718 764. 1998.
- 8.Sudsakorn K, Turton R. Non-uniformity of particle coating on a size distribution of particles in a fluidized bed coater. Powder Tech. 2000;110:37–43. doi: 10.1016/S0032-5910(99)00266-1. [DOI] [Google Scholar]
- 9.Shelukar S, Ho J, Zega J, et al. Identification and characterization of factors controlling tablet coating uniformity in a Wurster coating process. Powder Tech. 2000;110:29–36. doi: 10.1016/S0032-5910(99)00265-X. [DOI] [Google Scholar]
- 10.Stein M, Ding YL, Seville JPK, Parker DJ. Solids motion in bubbling gas fluidized beds. Chem Eng Sci. 2000;55:5291–5300. doi: 10.1016/S0009-2509(00)00177-9. [DOI] [Google Scholar]
- 11.Fitzpatrick S, Ding Y, Seiler C, et al. Positron emission particle tracking studies of a Wurster process for coating applications. Pharm Tech. 2003;27:70–78. [Google Scholar]
- 12.Cassanello M, Larachi F, Legros R, Chaouki J. Solids dynamics from experimental trajectory time-series of a single particle motion in gas-spouted beds. Chem Eng Sci. 1999;54:2545–2554. doi: 10.1016/S0009-2509(98)00468-0. [DOI] [Google Scholar]
- 13.Xu M, Turton R. A new data processing technique for noisy signals: application to measuring particle circulation times in a draft tube equipped fluidized bed. Powder Tech. 1997;92:111–117. doi: 10.1016/S0032-5910(97)03222-1. [DOI] [Google Scholar]
- 14.San Jose MJ, Olazar M, Alvarez S, Izquierdo MA, Bilbao J. Solid cross-flow into the spout and particle trajectories in conical spouted beds. Chem Eng Sci. 1998;53:3561–3570. doi: 10.1016/S0009-2509(98)00170-5. [DOI] [Google Scholar]
- 15.USP-NF. Physical tests, bulk density and tapped density. In: US Pharmacopeia-National Formulary. First Annual Asian Edition. 2002;616:1981–1982.
- 16.Wells J. Pharmaceutical preformulation. In: Aulton ME, editor. Pharmaceutics: The Science of Dosage Form Design. New York, NY: Churchill Livingstone; 2002. pp. 113–138. [Google Scholar]
- 17.Deasy PB. Air Suspension Coating. In: Deasy PB, editor. Microencapsulation and Related Drug Processes. New York, NY: Marcel Dekker; 1984. pp. 161–180. [Google Scholar]
- 18.Porter SC, Ghebre-Sellassie I. Key factors in the development of modified-release pellets. In: Ghebre-Sellasie I, editor. Multiparticulate Oral Drug Delivery. New York, NY: Marcel Dekker; 1990. pp. 217–284. [Google Scholar]