Grinding aids, effects

Additives can alter the rate of wet ball milling by changing the slurry viscosity or by altering the location of particles with respect to the balls. These effects are discussed under Tumbhng Mills. In conclusion, there is still no theoretical way to select the most effective additive. Empirical investigation, guided by the principles discussed earlier, is the only recourse. There are a number of commercially available grinding aids that may be tried. Also, a Idt of 450 surfactants that can be used for systematic trials (Model SU-450, Chem Service... 

Materials used as grinding aids include solids such as graphite, oleo-resinous liquid materials, volatile solids, and vapors. The complex effects of vapors have been extensively studied [Goette and Ziegler, Z. Ver. Dt.sch. Ing., 98, 373-376 (1956) and Locher and von Seebach,... 

Table IX Examples of the Effect of Grinding Aids in Dry and Wet Grinding Systems (21).

Many materials have been used as admixtures and the potential of many more has been examined. The literature, including the patent literature and other descriptions of proprietary materials, is voluminous a useful review published as long ago as 1980 includes over 600 references (M103). We shall only attempt to describe the effects of the most important classes of admixtures in general terms and to discuss the chemistry underlying those effects at a fundamental level. Grinding aids are similarly considered. 

The effect of some of these grinding aids on the fineness of cement after a specific grinding time is depicted in Fig. 5.58. It can be seen that with the exception of soot, the desired effect is produced only if the amount used is very small. At higher concentrations the agglomeration tendency increases due to the formation of adsorption layers and liquid bridges. In the case of soot a greater quantity is required because it is a solid which, as compared with molecules in the form of gas or vapor, is not very mobile. 

As a rule, grinding aids also reduce caking. Fig. 5.59 demonstrates the effect of... 

Fig. 5.58 Effect of some grinding aids" on the fineness of cement after grinding clinker for the same time in a rod mill.

InFig. 4.51 the effect of different grinding aids on the specific surface of cement is presented. As it is shown the poly-glycol-phenol ether and the heptane-phos-phonate acid have the strongest impact. The effectiveness of saturated fatty acids and alcohols action grows with the rednction of chains length, the undersaturated acids are more active than the saturated ones [152,153]. This can be explained by... 

Fig. 4.52 Effect of grinding aids on cement fineness (according to [151])...

In the grinding of many metals, reaction of the freshly cut metal surface with air forms an oxide layer which can effectively prevent adhesion of the metal surface to the abrasive, to the bond, or to itself. This facilitates the abrasive process. Substances which can react more rapidly with fresh metal surfaces than does air, or which can melt and cover the surface with a protective layer, are called active grinding aids. The most common ways such substances are used is in the oils or water-based coolants for wet grinding and as impregnants or fillers in the bond of the abrasive article for dry grinding. 

Pigment Dispersion. The alkan olamines and thek derivatives are useful in dispersing titanium dioxide and other pigments (209). Monoisopropanolamine and triethanolamine are particularly effective in aiding titanium dioxide dispersion in the production of Ti02 and in water-based paints (210). The alkan olamines are also an aid in the grinding of titanium dioxide (211). 

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