Grinding fluid concentrates

Miscellaneous. Volatile nitrosamines can escape into the atmosphere from a variety of other sources. Automobile and diesel engine exhausts may contain N-nitroso compounds, including NDMA at trace levels (5). Nitrosodiethanolamine (NDEIA) is a likely air contaminant in machine shops which use cutting and grinding fluids contaminated with high concentrations of NDElA (10). Several herbicides, known to contain appreciable levels of volatile nitrosamines (9), are applied as aqueous sprays it is likely that worker exposure via inhalation may be appreciable. 

Cutting and grinding fluids, emulsifiable concentrates, asphalt emulsions. 

The general pieces of equipment used in grinding flake mica or mica concentrate into saleable mica products are hammer mills of various types, fluid energy mills, Chaser or Muller mills for wet grinding, and Raymond or WiUiams high side roUer mills. Another method is being developed, called a Duncan mill (f. M. Huber, Inc.), that is similar in many respects to an attrition mill. AH of these mills are used in conjunction with sieves, and all but some types of hammer mills incorporate air classifiers as a part of the circuit. 

In wet grinding the power consumption is generally about 30 per cent lower than that for dry grinding and, additionally, the continuous removal of product as it is formed is facilitated. The rheological properties of the slurry are important and the performance tends to improve as the apparent viscosity increases, reaching an optimum at about 0.2 Pa.s. At very high volumetric concentrations (ca. 50 volume per cent), the fluid may exhibit shear-thickening behaviour or have a yield stress, and the behaviour may then be adversely affected. 

The manufacturing factors that may be affected by the choice of a particular polymorphic form include granulation, milling and compression, stability (particularly for semisolid forms), amount of dose delivered in metered inhalers, crystallization from different solvents at different speeds and temperature, precipitation, concentration or evaporation, crystallization from the melt, grinding and compression, lyophilization, and spray drying. In the manufacturing processing, crystallization is a major problem and it can be avoided by a careful study of polymorphic transition, particularly in supercritical fluids. 

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