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 polyethyl ene-bound abrasive calcite agglomerates. Water soluble polymers are us ed to agglomerate the needle-like crystals of tetraacetylethylene diam ine and also sodium chloride crystals. In a typical isothermal FIPI ag glomeration process primary particles are dispersed in the molten bind er, which is subsequently inverted by the addition of sufficient amoun t of primary particles, which also defines the critical filler concent ration at phase inversion, C(c). Agglomerate particle size is primaril y a function of C(p) - C(c) where C(p) is the mean concentration of fi ller. C(c) decreases with increasing binder molecular weight and prima ry 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 dist ribution, binder concentration distribution in each agglomerate size r ange, agglomerate topology, binder morphology in the agglomerates, agg lomerate strength, and agglomerate dissolution rate in water were eval uated. These agglomerate characteristics are related to the binder and filler properties as well as to the processing conditions.