(667f) Coating of Fine Particles: Moving from Supercritical Fluid Technology and Fluid-Bed Coating to Novel Solventless Technology

Coating of solids is an essential process for a diverse group of industries including the chemical, pharmaceutical, agricultural, cosmetic, electronic, and food. Unfortunately, most industrially relevant coating processes require use of solvents and are not generally suitable for coating very fine particles without significant agglomeration. Thus the coated particle size and the use of solvents remain two major barriers to pushing the limits of the coating methodology. My collaboration on this topic with Prof. Pfeffer began over a dozen years ago when we first started addressing the size barrier. In this talk, first the early work using supercritical fluid technology will be summarized where we showed that the antisolvent process was capable of coating particles having nano and micro sizes. Later, film-coating of Geldart group C powders was demonstrated using either centrifugal or conventional fluidization. Most recently, NJIT team has introduced a dry-coating methodology by which microparticles can be coated with polymers without the use of solvents, plasticizers, or heat treatments. This novel methodology is applicable to particles including those < 100 μm, noted as major improvements upon solvent-based and current dry-polymer coating technologies. In this novel dry-polymer-coating method, high intensity vibratory mixing device is used to first form an ordered mixture consisting of a particulate substrate, which is subsequently processed further to form a conformal polymeric film. As an example, challenging material such as ascorbic acid (AA) that is brittle and cannot withstand very large mechanical forces is considered. AA particles, ranging in size from 50 µm to 500 µm are successfully coated with a micronized polymer, polyethylene (PE) wax.  Polymer coatings were able to prolong the dissolution time of ascorbic acid from seconds to hours depending on the coating thickness. Overall, this is a major advance that is part of the legacy of work inspired by Prof. Pfeffer.