Water-Soluble Cellulose Derivatives as Coating Agents in Fluidized Bed Processing

Abstract

The quality of a particle coating is strongly affected by both the parameters of the fluidized bed process and the properties of coating materials. Within this research, the effect of solution properties (viscosity of the coating solution, coating solution droplet size) on the quality of coatings obtained from three water-soluble cellulose derivatives (methylcellulose, carboxymethylcellulose, and hydroxypropylcellulose) was investigated. Coating quality was quantified using confocal laser scanning microscopy (CLSM). The results showed a pronounced effect of viscosity on the quality of methylcellulose and carboxymethylcellulose coatings. The best results for methylcellulose coatings were obtained when the least concentrated and at the same time least viscous solution was sprayed onto the fluidized particles. In the case of carboxymethylcellulose the best results were obtained using an intermediate (5 w/v %) concentrated coating solution. The quality of the hydroxypropylcellulose coatings was not influenced by the coating solution viscosity and presented very similar values after performing all fluid bed experiments. For the materials covered in this work, the best coating quality was obtained for hydroxypropylcellulose. The least uniform coatings with the highest number of coating deficiencies and highest degree of agglomeration of coated beads were found for carboxymethylcellulose.

Keywords:

• coating quality
• coating solution properties
• fluidized bed coating
• microencapsulation
• water-soluble cellulose derivatives

This research was funded through the Marie Curie Research Training Network “Biopowders” of the EU 6th Framework Programme (MRTN-CT-2004-512247).