Purpose: To evaluate the attainable coating speed of a high productivity, ultra-high solids coating system which is designed to achieve high gloss and improved aesthetics in a high speed semi-continuous Consgima coater (GEA Systems). This coating technology was developed to coat small 3-6 kg lots very rapidly with a high degree of efficiency on a continuous processing line (10-100 kg/hr).
Methods: Aqueous dispersion's of the fully formulated system were prepared for rheological assessment. The coating was evaluated at varied concentrations and process parameters to determine optimum conditions that yielded the best efficiency while maintaining tablet coating quality. Round shape, 450 mg, placebo tablets were used as the coating substrate (3 kg batch size). The coating trials (28) were conducted in the ConsiGma coater fitted with a 160 mm wheel. DOE methodology was used to evaluate the effect of spray rate (40-80 gm/min), inlet temperature (75°C-85°C), and solids (25%-35%) on the surface roughness, gloss and color uniformity of the coated tablets. The tablets were sampled at the end of 3% weight gain and tested for color uniformity using a reflectance spectrophotometer (DataColorTM 650), surface roughness evaluation using an optical profilometer (NanoveaTM) and tablet gloss was measured using a surface analysis system (Tricor SystemsTM).
Results: The coating system exhibited desirable viscosity even at high solid concentration (Figure 1). Depending on the spray rate and solids concentration levels, a 3% weight gain of coating was achieved in as little as 3 minutes or as long as 9 minutes. In most cases, the new system had low surface roughness (< 5 sq. µm), high gloss (> 100 gloss units) and color uniformity <1.2 ΔE from 2.0% weight gain. (Figure 2). This data clearly exemplifies the exceptional mixing efficiency of tablets in the wheel using this coating technology.
Conclusion: Overall, the appearance of the coated tablets was very impressive even when coated at high solids (35%). The high solid concentration of this developmental coating in addition to the unique design and process of the ConsiGma coater enabled faster application of the material on the tablet cores. The entire 28 run DOE was conducted in less than two (2) days while utilizing only 84Kg of the material. The resultant coated tablets exhibited excellent aesthetics and color uniformity.
Thomas Dürig– Senior Director, Ashland Specialty Ingredients, Wilmington, Delaware
Ronald Hach– Ashland Specialty Ingredients
Andrew Birkmire– GEA Pharma Systems, Maryland
Erica Anderson– GEA Pharma Systems, Maryland
Jessica Zombek– GEA Process Engineering, Inc.