FLOW-INDUCED PHASE INVERSION AGGLOMERATION - FUNDAMENTALS AND BATCH PROCESSING

A novel agglomeration technique, based on flow induced phase inversion (FIPI) is described and applied to the batch preparation of polyethylene-bound abrasive calcite agglomerates. Water soluble polymers are used to agglomerate the needle-like crystals of tetraacetylethylene diamine and also sodium chloride crystals. In a typical isothermal FIPI agglomeration process primary particles are dispersed in the molten binder, which is subsequently inverted by the addition of sufficient amount of primary particles, which also defines the critical filler concentration at phase inversion, C(c). Agglomerate particle size is primarily a function of C(p) - C(c) where C(p) is the mean concentration of filler. C(c) decreases with increasing binder molecular weight and primary particle surface area. Agglomerate size distribution is affected by processing, mainly by the mixing time after phase inversion. For the non-isothermal FIPI agglomeration process, phase inversion is induced locally, by the addition of fine particles in the molten binder. Phase inversion is then propagated by cooling the dispersion during mixing. Agglomerate characteristics such as particle size, particle size distribution, binder concentration distribution in each agglomerate size range, agglomerate topology, binder morphology in the agglomerates, agglomerate strength, and agglomerate dissolution rate in water were evaluated. These agglomerate characteristics are related to the binder and filler properties as well as to the processing conditions.