An Alternative Banding Method For HPMC Liquid Filled Hard Shell Capsule
To evaluate the HPMC banding process and morphology using different banding agents, and compare HPMC banding and regular gelatin banding processes. To look for a possible new water based HPMC banding process and banding agent to replace the current alcohol/water based HPMC banding.
Hydroxypropyl methylcellulose (HPMC) is produced by synthetic modification of the natural polymer cellulose and is used as shell material for two piece hard shell capsules. HPMC capsules are considered to be an attractive alternative to gelatin capsules because of its vegetable source and little chance for crosslinking. To avoid leakage of the liquid formulation, or sometimes even solid formulation, through the gap between the cap and body of two piece hard shell capsules, capsules are usually sealed by banding the junction between the cap and body by using a banding agent. Gelatin capsule banding agents are water based gelatin solutions with a small amount of surfactant added. The gelatin solution melting point is at approximately 35ºC. The banding solution is kept warm and in a liquid state during banding, and turns to a gel after the band is applied. For HPMC capsule banding, usually the HPMC powder is dissolved in ethanol /water solution and capsules are banded at room temperature. The ethanol content is over 50 wt%. Since the banding solution chamber in the banding machine is not sealed, and the band drying tower is open to the process room, during the banding and drying process, a significant amount of flammable alcohol vapor will be released to the process room. Furthermore, in this two-solvent banding agent, ethanol evaporates faster than water. After the banding process proceeds for a certain amount of time, solvent dosing becomes necessary to keep the solution viscosity at a constant level and to control the HPMC amount at a constant percentage. The two- solvent system makes this dosing process difficult, since a simple solution viscosity test is not able to measure the ethanol/water ratio in solution. For these reasons several other candidates for water based HPMC banding agents and processes have been tried. Among them, a gelatin water solution is a successful banding agent for gelatin capsules. HPMC water solution is a purified water based solution. The most interesting banding agent is the HPMC solution containing a small amount of gelling agent.