High shear mill

Fluid mixers, high shear mills, pumps... 

Milling High-shear milling (Fitz milling) Continuous process... 

Milling High-shear milling/cryogrinding with and without excipients, e.g.. Biorise ... 

Many methods for the conversion of acid copolymers to ionomers have been described by Du Pont (27,28). The chemistry involved is simple when cations such as sodium or potassium are involved, but conditions must be controlled to obtain uniform products. Solutions of sodium hydroxide or methoxide can be fed to the acid copolymer melt, using a high shear device such as a two-roU mill to achieve uniformity. AH volatile by-products are easily removed during the conversion, which is mn at about 150°C. A continuous process has been described, using two extmders, the first designed to plasticate the feed polymer and mix it rapidly with the metal compound, eg, zinc oxide, at 160°C (28). Acetic acid is pumped into the melt to function as an activator. Volatiles are removed in an extraction-extmder which follows the reactor-extmder, and the anhydrous melt emerges through a die-plate as strands which are cut into pellets. 

Two-Roll Mills These mills contain two parallel rolls mounted in a heavy frame with provision for accurately regulating the pressure and distance between the rolls. As one pass between the rolls does little blending and only a small amount of work, the mills are practically always used as batch mixers. Only a small amount of material is in the high-shear zone at any one time. 

As a consequence of the high shear rate to which the rubber is subjected at the nip of the mill crystallization occurs at temperatures of up to 80 °C in compounds based on SE-BR and U-BR, and this phenomenon is responsible for the improvement in the processing behaviour. 

For any given size of mill there is a minimum volume of polymer per unit width of roll, below which no dispersive mixing occurs. Increasing the amount of material above this minimum level increases the high shear zone in the polymer, increasing dispersive mixing. There is an upper limit however, above which a circulatory flow develops at the entrance to the nip region and no further improvement occurs. 

Average temperatures (40-70°C) in combination with high-shear dispersion equipment, of which three-roll mills are a good example, appear to afford the best results in terms of pigment dispersion in wetting systems, such as offset varnish. Fig. 33 shows a curve in which the degree of dispersion reaches a distinct maximum at one particular temperature. 

During the production of paint, it is important to keep control of the temperature. Due to the high shear forces a substantial amount of heat is produced especially in the pearl mill. Some ingredients in the paint are sensitive to heat, e.g. solvents which will have the risk to flash off. Therefore additional cooling is normally needed in this operation. Figure 9 shows a flow diagram of paint production in a factoiy. 

Processes which melt mix polymer and filler are capable of generating the high shear stresses necessary to cause agglomerate break up, together with re-distribution of the primary filler particles. Since its conception in 1835, the two-roll mill has proved to be an effective means of mixing additives into plastics and rubber and is still in widespread use today, principally for laboratory purposes, but to some extent in large-scale industrial applications. 

Figure 15 shows a fluidized bed dryer vertically integrated with a high-shear granulator, a wet mill, bottom discharge, and a dry mill. The basic components of the machine will be described, beginning with the entrance of the... 

Figure 15 Fluid bed dryer with integrated high-shear granulator and mills.

Mix Part A with a high-shear mixer (Colloid Mill or Eppenbach mixer). 

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