Processes stereospecific emulsion

Solution polymerization is bulk polymerization in which excess monomer serves as the solvent. Solution polymerization, used at approximately 13 plants, is a newer, less conventional process than emulsion polymerization for the commercial production of crumb mbber. Polymerization generally proceeds by ionic mechanisms. This system permits the use of stereospecific catalysts of the Ziegler-Natta or alkyl lithium types which make it possible to polymerize monomers into a cis structure characteristic that is very similar to that of natural rubber. This cis structure yields a rubbery product, as opposed to a trans stmcture which produces a rigid product similar to plastics. 

Even though monomers are generally quite reactive (polymerizable), they usually require the addition of catalysts, initiators, pH control, heat, and/or vacuum to speed and control the polymerization reaction that will result in optimizing the manufacturing process and final product.74 When pure monomers can be converted directly to pure polymers, it is called the process of bulk polymerization, but often it is more convenient to run the polymerization reaction in an organic solvent (solution polymerization), in a water emulsion (emulsion polymerization), or as organic droplets dispersed in water (suspension polymerization). Often choose of catalyst systems exert precise control over the structure of the polymers they form. They are referred to as stereospecific systems. 

A chain polymerization can be radicalar, anionic, cationic, or stereospecific according to the type of initiator used. The reaction may occur in bulk, in suspension, in emulsion, as in solution. It is necessary to choose adequate temperatures for a good control of the processes. 

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