General Features of Continuous Emulsion Polymerization Processes

1 General Features of Continuous Emulsion Polymerization Processes 

Continuous emulsion polymerization processes have been widely used in the large-scale production of latex products. For example, styrene-butadiene rubber latex products are manufactured by such processes consisting of a 

Reactor configurations involved in continuous emulsion polymerization include stirred tank reactors, tubular reactors, pulsed packed reactors, Couett-Taylor vortex flow reactors, and a variety of combinations of these reactors. Some important operational techniques developed for continuous emulsion polymerization are the prereactor concept, start-up strategy, split feed method, and so on. The fundamental principles behind the continuous emulsion polymerizations carried out in the basic stirred tank reactor and tubular reactor, which serve as the building blocks for the reaction systems of commercial importance, are the major focus of this chapter. 

Just like a batch reactor, all the reacting species in an idealized tubular reactor have exactly the same residence time. Thus, the mechanisms and kinetics presented in Chapters 3 and 4 are also applicable to emulsion polymerization carried out in a tubular reactor. On the other hand, the feed stream introduced into a continuous stirred tank reactor at any given time becomes completely mixed with the reaction mixture already present in the reaction system. As a result, a distribution of residence times of the material within a continuous stirred tank reactor is achieved. In other words, some of the recipe ingredients entering the continuous stirred tank reactor may leave it almost immediately because material is continuously withdrawn from the reactor. In contrast, other recipe ingredients may remain in the reactor almost forever because all the material is never removed from the reactor at one time. Many of the reaction species leave the reactor after spending a period of time somewhere in the vicinity of the mean residence time. The distribution of residence 

Rgure 7.3. A schematic representation for a continuous emulsion polymerization process, in which the relatively monodisperse particle size distribution of seed latex particles introduced into a continuous stirred tank reactor becomes broader at the exit of the reactor. 

---