microscale level of the polymerization process. The most important point is to
avoid overheating of these particles by the highly exothermic polymerization
reaction. As described by Wicke et al. [29–31], there are different stable points
for such microreactors (Fig. 6).
To avoid any overheating of this microreactor or growing polymer particle, the
temperature of the particle must remain at the lower stable reaction point (T min )
close to the temperature of the surrounding diluent (T 0 ). Then the process is
kinetically controlled. At the upper stable reaction point (T max ), the temperature
of the growing particle is much higher than the diluent temperature (T 0 ) and the
process is diffusion controlled. For the technical process, it is of great importance
that all microreactors always run at the lower stable reaction point (Fig. 7).
macroscale level
mesoscale level
microscale level
gas bubble
polymer particle
Fig. 4 Scheme for modeling the slurry polymerization process
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. . .
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. . . .. .
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. . . . . .
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catalyst particle
20 µm
450 µm
primary particle
polymer particle
1 µm
polymerization
Fig. 5 Particle-forming process
66
L.L. Bo ¨hm