F. Louis Floyd
The above references are excellent in providing an overview.
I would reiterate that this process is part of a generalized approach that involves taking a high polymer in solution in a water-miscible solvent, then adding water slowly and with mixing to cause a phase inversion into a water-based dispersion. By distilling off the cosolvent, solvent-free end products can be achieved.
The phase inversion process has several notable features:
- provides the smallest, most uniform particle size for a given system
- viscosity goes through a maximum during phase inversion. That maximum can be quite high, and may cause a loss of mixing. Thus, the lower the viscosity of the solution, the better (optimum would be that of water). The solution viscosity will depend on the molecular weight and concentration of the polymer in the solvent.
- Foaming/defoaming tends to be ineffective during the inversion process, due to the maximum in viscosity that occurs at that point. Corrective action is best taken well-away from the phase inversion composition, where viscosity is more tractable.
- often requires the use of external surfactants to achieve post-inversion stability
- stability may be enhanced by the incorporation of acid functionality in the polymer backbone -- but that must be balanced by the water sensitivity that will be introduced by such functionality
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