(443g) Using Magnetically Assisted Impact Coating (MAIC) for Optimization of Powder Flow Characteristics

Many processes need to control powder flow in order to improve processing and maintain consistent product quality. Typical methods for control of powder flow involve the addition of flow aids, with few process handles except the amount of flow aid added to the powder. Typical flow aids used in this manner are fumed silica, a hydrophilic flow aid, and magnesium stearate, a hydrophobic flow aid.

Magnetically Assisted Impact Coating (MAIC) has been demonstrated as a technique for coating host particles without causing major changes to particle shape and size, which creates for a unique method for the application of flow aids [1]. This system relies on a process in which an oscillating magnetic field is used to accelerate and spin large magnetic particles, causing the magnetic particles to fluidize. The agitated magnetic particles impart energy to a substrate and its flow aid, and coating is then achieved as collisions occur between particles and between particles and the vessel wall [1].

MAIC has shown to improve flow properties of a model compound, 5 μm citric acid, both with and without the addition of a hydrophilic fumed silica flow aid [2], and has been shown to improve the flow properties better than traditional mixing methods. In addition to changing the amount of flow aid added to a powder, the MAIC process has a number of different process parameters that can affect powder flow. The goal of this presentation is to offer a systematic analysis of the various process parameters, with a focus on the difference between batch [1] and continuous MAIC processing, residence time, intensity, and substrate effects. Additionally, a hydrophobic fumed silica will be compared with the original hydrophilic fumed silica with respect to their influence on powder flow properties. Powder flow measurements are done with an FT4 Powder Rheometer®, and include dynamic, bulk, and shear properties [3]. The study is ongoing, and the data are currently preliminary. Statistical comparisons of the flow properties will be presented.

References

[1] Ramlakhan, M., Wu, C.Y., Watano, S., et al., Dry particle coating using magnetically assisted impaction coating: Modification of surface properties and optimization of system and operating parameters. 2000:112:137-148.

[2] Freeman, T; Hendrickson, W.; Bowman, C. R. et al. (2016, November). Comparison of Magnetically Assisted Impact Coating (MAIC) with Traditional Mixing Techniques for the Addition of a Silica Flow Aid. Paper presented at the meeting of the American Institute of Chemical Engineers, San Francisco, CA.

[3] Brockbank, K., Armstrong, B., Chandorkar, Y., et al., Understanding powder caking as a consequence of a range of mechanisms by means of powder rheometry. 2015:33:102-108.