Dispersion milling mill charging

Mill base n. The portion of the coating formulation which is charged in the dispersion mill. 

One study of this interaction that we performed involved the use of polyvinyl butyral and two different dispersants, menhaden fish oil and phosphate ester. Batches were charged identically, with the exception of the dispersant. One batch was formulated with 4 wt% menhaden fish oil per powder weight, while the other was formulated with 2 wt% phosphate ester per powder weight. After dispersion milling, the MFO batch was very viscous, almost a paste (>20,000 cP), while the phosphate ester batch was extremely fluid (<100 cP). After identical plasticizer and binder additions, the slips were measured to have identical viscosities (approximately 2500 cP). In the MFO batch, the binder s dispersing action far overshadowed the fluidizing action of the MFO. Conversely, the phosphate ester was seen to be a much better dispersant/deflocculant than the MFO. The tapes cast from these slips were nominally identical, as were the fired densities and yields. 

Dispersion mill Jar mill charged with solvent, dispersant/defloc-culant, and powder. This milling step is done for the sole purpose of creating a dispersion of the powder in the solvent vehicle. The term implies that binder and plasticizer have not yet been added to the slip. 

The second class of grinding equipment is used to prepare dispersions. Typical of this class are baU and pebble mills, ultrasonic mills, and attrition mills. SoHds, eg, sulfur, antioxidants, accelerators, and zinc oxide, are generaUy ground on this equipment (see Size reduction). BaU mill action is assisted in some mills by a combination of dispersion circulation by an external pump and mechanical osciUation of an otherwise fixed nonrotary mill chamber. Where baU mill chambers are rotated it is necessary to experimentally estabHsh an optimum speed of rotation, the size and weight of the baU charge, and ensure the mills do not overheat during the grinding period. 

The second path in Fig. 3 outlines the approach to a more robust tape designed by Drew [21]. Here the milled rubber and filler are combined with tackifiers and other additives/stabilizers in an intensive dispersing step, such as a Mogul or Banbury mixer. Next, a phenolic resin or an alternative crosslinker is added and allowed to react with the rubber crosslinker to a point somewhat short of crosslinking. The compounded mixture is then charged to a heavy duty chum and dissolved in a suitable solvent like mineral spirits. To prepare a masking tape. 

Fig. 3 The media milling process is shown in a schematic representation. The milling chamber charged with polymeric media is the active component of the mill. The mill can be operated in a batch or a recirculation mode. A crude slurry consisting of drug, water, and stabilizer is fed into the milling chamber and processed into a nanocrystalline dispersion. The typical residence time required to generate a nanometersized dispersion with a mean diameter <200 nm is 30-60 min. (From Liversidge, E.M. Liversidge, G.G. Cooper, E.R. Eur. J. Pharm. Sd. 2003,18, 113-120).

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