(663f) Effect of Feed Frame Design and Operating Parameters On the Powder Hydrophobicity and Flow Properties

Authors: 
Mendez-Roman, R., Rutgers University
Muzzio, F. J., Rutgers University
Velazquez, C., University of Puerto Rico, Mayaguez Campus


Powder flowability is affected both by powder material properties and by the equipment used for processing the material. This dependence of powder flow properties on multiple variables is important for the effective manufacturing of compacts in the pharmaceutical, food, agrochemical, cosmetics, and consumer product industries. In all of these applications, consistent flow of powders into the small die of a tablet press is key to producing tablets with consistent properties.

Manufacturers often use mechanical devices, called ?feed frames? or ?feed shoes? to maintain an adequate supply of powder to fill the dies of the tablet presses. Interestingly, the almost no published work on these critical devices is available. Our work focuses on studying the effect of the feed frame speed, die table speed, and material properties on the powder flow behavior when moving into the dies. In particular, we focus on one of the effects commonly referred to as ?overlubrication?, which is characterized by decreased tablet dissolution and restricted drug bioavailability often observed when the process is scaled up.

Pharmaceutical powders are typically lubricated using friable hydrophobic components (most commonly MgSt), and it is well known that flow and compression properties of blends containing this material can be shear sensitive. Since powders experience significant mechanical work as they flow through a feed frame, we also examined the effect of shear and strain on the hydrophobicity of the treated powders. Different powder blends with and without lubricant and with or without an active ingredient (acetaminophen) were tested. Results readily demonstrated that the hydrophobicity of lubricated pharmaceutical powders can increase significantly as they travel across the feed frame, and that the effects are dependent both on the feed frame speed and the rotating table speed, possibly helping understand one of the mechanisms for overlubrication.