Relative Importance of the Effects of Seed and Feed Stage ...

Seed and Feed Stage Agitations of BMA and NMA 375
Figure 5.
conditions.
The amount of water-soluble species in the latexes for different agitation
stages), the BMA monomer started to form a pool at ca. 60 min of the feed
stage, and by ca. 80 min, a ca. 0.5 cm monomer layer accumulated at the
top of the reactor. The solids content in the final latex was ca. 23 wt%.
Figure 5 compares the amount of water-soluble species in the serum formed
when the 4 cm agitator was used, with those in the latexes prepared using
the 8 cm agitator. Clearly, the amount of water-soluble solids is higher.
Thus, a poor emulsification of the BMA monomer results in a slower rate
of transfer of the BMA monomer to the polymer particles. The proportion
of the added NMA monomer that homopolymerizes, is greater compared to
the amount copolymerizing with BMA. Thus, a greater amount of watersoluble
polymer is formed.
The frequency at which the fluid recirculates through the agitator
region is proportional to ND 3 . Thus, the fluid passed through the agitator
region less frequently with the 4 cm agitator than with the 8 cm agitator.
Emulsification of the added BMA occurs in the high-shear agitator region.
The size of the BMA droplets will be lower with a higher shear rate in the
agitator region, and more frequent recirculation through this region. Thus,
the BMA droplets produced by the 4 cm agitator will be larger compared
to those produced by the 8 cm agitator. The surfactant coverage of the
polymer particles and the monomer droplets decreases during the feed stage
because of growing surface area (and no added surfactant). The monomer
droplets rise to the surface of the reactor and coalesce to form a pool.