Technical Implications of Organic Syntheses in Ball Mills - Ball Milling Towards Green Synthesis: Applications, Projects, Challenges - page 246

or additives, (iii) the reagent ratio, and (iv) the presence of low amounts of
liquid(s) in the case of liquid-assisted grinding, LAG. 40,42-46
With respect to technological parameters, the importance of (i) the type of
ball mill, (ii) the milling material, (iii) the number and (iv) size of milling
balls as well as (v) the filling degree of the milling beakers for the accom-
plishment of chemical reactions should be considered. This set of par-
ameters describes the technology that is used for comminution.
Process parameters are useful for controlling the energy entry during the
process. The main values in this class of parameters are (i) operating fre-
quency (rpm), (ii) reaction time (t reaction ), and (iii) temperature (T). Whereas
rpm is directly correlated to the kinetic energy of the grinding media and,
thus, to the energy that can be dissipated as heat to the mill charge, t reaction
and T determine the progression of a chemical reaction and are linked to the
reaction kinetics.
10.3 Technological Parameters
This first set of parameters describes the technology that is used for the
comminution, such as type of ball mill, grinding material, number and size
of the milling balls as well as the filling degree of the milling beakers.
10.3.1 Type of Ball Mill
Particle refinement technology includes various types of ball mills for ap-
plications in industry and at laboratory scale. 9,30,31,47 From the large number
of technical possibilities for the realization of mechanical action of grinding
bodies to a mill feed, only a manageable number has been applied so far for
organic synthesis on the laboratory scale. 10,48 The main types of ball mills
used so far for synthetic purposes and their working principles are sum-
marized in Figure 10.2. 49 Figure 10.3 provides a general overview of the
existing technologies applicable for mechanochemical reactions of solids on
laboratory to (pilot) plant scale. 50 Beside differences in the operating prin-
ciple they differ in the maximum capacity of the milling vessel, V MV,max ,
ranging from 0.010 L for planetary (PBM), mixer (MBM) or vibration ball
mills (VBM) to several 100 L for horizontal rolling ball mills.
10.3.1.1 Planetary Ball Mills
Planetary ball mills (PBMs, Figure 10.3B) are a special form of drum mills
used, for example, in the ore refining industry at large-scale levels (see for
instance Figure 10.3D). A PBM is a device by which on a central disk (sun
disk) disks of smaller diameter are mounted containing the holding mech-
anism(s) for the milling beakers, whereby the number of vessels is 1, 2 or 4.
The disks rotate in opposite directions and, therefore, the movement of the
milling beakers is similar to the rotation of a planet around their central
celestial body in the sun system. 49,51,52 The grinding bodies inside the