(135b) Online Pellet Drying for Inline Polymer Analysis

Hook, B. D., The Dow Chemical Company
Braun, B., The Dow Chemical Company
Dhodapkar, S., The Dow Chemical Company
Some polymers extrude with high levels of moisture-holding cracks. This phenomena, often called melt fracture, makes drying of these particles particularly difficult. At-line or in-line analyses of polymer pellets using film extrusion, for example, require moisture-free streams of pellets on a continuously feeding basis. The low feed rate of most sampling systems, however, means that industrial scale dryers are not appropriate. Similarly, such a dryer should be able to give close to a first-in/first-out or plug flow residence time characteristic with as little backmixing as possible. A prototype-sampling device has been developed based upon first principles. The novel drying device utilizes a cyclone separator combined with a fluidized bed to rapidly dry the pellets prior to cast film analysis. Initial results from the novel drying system applied to polyethylene applications suggest that it may be superior to pellet drying using currently practiced technology. Details of the design, testing and evaluation of the dryer will be presented.