Experiments and numerical modeling to estimate the coating variability in a pan coater.

The purpose of this work is to investigate the effect of the coating process parameters on coating performance and coating variability, and hence determine the optimal operating conditions. Coating of particles is done to mask the unpleasant taste or odor of the drug, to control the bioavailability of the API, and to increase shelf-life. The coating solution is sprayed in specific locations of the granular bed and coating uniformity is achieved by interparticle collisions and overall mixing behavior in the coater. Thus, good understanding of particle flow and granular mixing in a pan coater is vital to optimize the process parameters to reduce coating variability. Coating experiments are performed at previously determined optimal mixing conditions using Lactose nonpareils. The coating fluid (aqueous solution of Opadry II) is sprayed intermittently at different flow rates and concentration. Vernier Caliper is used to measure the change in diameter and the coating of the particles. Moreover, DEM based numerical modeling of spray coating is also performed for same operational parameter set and spray characteristic (center and the radius of the spray zone) used in the experiments. DEM simulation provides the residence time distribution of all the particles passing through the spray zone. The coating variability in the experiments is estimated at different pan and spray variables. The coating variability decreases with the increase inpan tilt, coating time and an optimum speed. The spray characteristics does not seem to have much effect on the variability although better coating is observed under better mixing conditions of high tilt and pan speed for the same spray parameters. The mass distribution of coated particles is quantified in the numerical model by the total number of particles passing through the spray zone and also by the frequency distribution of the residence time of the coated particles. It is observed that the simulations are in good agreement with the experiments for the effect of orientation (tilt) of the pan coater on coating variability. However simulations over predicted the effect of speed as compared to the experiments to reach the minimum coating variability. In the current study, the experimental setup did not reflect the typical bead coating setup used in the industry; rather depict a simplified setup to validate the numerical model.

[1]  Nitin Joshi,et al.  Mathematical Model to Predict Coat Weight Variability in a Pan Coating Process , 2007, Pharmaceutical development and technology.

[2]  Julio M. Ottino,et al.  Transverse flow and mixing of granular materials in a rotating cylinder , 1997 .

[3]  P. Skultety,et al.  Quantitation of the Amount and Uniformity of Aqueous Film Coating Applied to Tablets in a 24″ Accela-Cota , 1988 .

[4]  Richard Turton,et al.  Modeling weight variability in a pan coating process using Monte Carlo simulations , 2006, AAPS PharmSciTech.

[5]  R. Chang,et al.  The Effect of Run Time on the Inter-Unit Uniformity of Aqueous Film Coating Applied to Glass Beads in a Hi-Coater , 1995 .

[6]  R. L. Braun,et al.  Viscosity, granular‐temperature, and stress calculations for shearing assemblies of inelastic, frictional disks , 1986 .

[7]  B Buisson,et al.  A model of surface renewal with application to the coating of pharmaceutical tablets in rotary drums , 2003 .

[8]  Richard J. Bathurst,et al.  Micromechanical features of granular assemblies with planar elliptical particles , 1992 .

[9]  Bodhisattwa Chaudhuri,et al.  Understanding granular mixing to enhance coating performance in a pan coater: Experiments and simulations , 2011 .

[10]  Carl Wassgren,et al.  Inter-tablet coating variability: Tablet residence time variability , 2009 .

[11]  Carl Wassgren,et al.  Inter-tablet coating variability: Residence times in a horizontal pan coater , 2008 .

[12]  Richard Turton,et al.  In situ, near real-time acquisition of particle motion in rotating pan coating equipment using imaging techniques , 2004 .

[13]  KuZilati KuShaari,et al.  Monte Carlo simulations to determine coating uniformity in a Wurster fluidized bed coating process , 2006 .

[14]  Dominic F. Sherony.  A model of surface renewal with application to fluid bed coating of particles , 1981 .

[15]  Richard Turton,et al.  Challenges in the modeling and prediction of coating of pharmaceutical dosage forms , 2008 .

[16]  Eiichi Abe,et al.  Coating mass distributions of seed particles in a tumbling fluidized bed coater Part II. A Monte Carlo simulation of particle coating , 1998 .

[17]  D. Prater,et al.  A MODEL SYSTEM FOR THE PRODUCTION OF AQUEOUS TABLET FILM COATINGS FOR LABORATORY EVALUATION , 1980 .

[18]  Richard Turton,et al.  Simulation of particle movement in a pan coating device using discrete element modeling and its comparison with video-imaging experiments , 2006 .

[19]  Kenji Yamane,et al.  Computer Simulation of Tablet Motion in Coating Drum , 1995, Pharmaceutical Research.

[20]  P Kleinebudde,et al.  A simple method for evaluating the mixing efficiency of a new type of pan coater. , 2001, International journal of pharmaceutics.

[21]  U. Mann.  Analysis of spouted-bed coating and granulation. 1. Batch operation , 1983 .

[22]  P. Cundall,et al.  A discrete numerical model for granular assemblies , 1979 .

[23]  R. Turton,et al.  The Prediction of Variability Occurring in Fluidized Bed Coating Equipment. II. The Role of Nonuniform Particle Coverage as Particles Pass Through the Spray Zonemr , 2000, Pharmaceutical development and technology.

[24]  R C Rowe,et al.  A photometric analysis of tablet movement in a side‐vented perforated drum (Accela‐Cota) , 1985, The Journal of pharmacy and pharmacology.

[25]  Troy Shinbrot,et al.  Experimentally validated computations of flow, mixing and segregation of non-cohesive grains in 3D tumbling blenders , 2000 .

[26]  Brahmeshwar Mishra,et al.  The discrete element method for the simulation of ball mills , 1992 .

[27]  G. L. Fourman,et al.  Assessing the uniformity of aqueous film coatings applied to compressed tablets , 1995 .