Polyreactions in bulk

Polyreactions in bulk are divided into homogeneous and heterogeneous reactions, depending on whether the polymer remains dissolved in its monomer or not or, respectively, whether the polyreaction is performed above or below the softening temperature of the polymer. 

Polyreactions in bulk are carried out without solvents or diluents. In this way, high molecular weights can be obtained frequently with high rates of reaction. The resulting products are very pure, because only monomers and, if necessary, initiators and catalysts are added. Polyreactions in bulk are also advantageous for economical and ecological reasons because recycling and purification of solvents or dispersants as well as the disposal of liquid waste (as in the case of aqueous suspension or emulsion polymerizations) are not necessary. On the other hand. 

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The basic characteristics as well as some advantages and disadvantages are illustrated in Sects. 2.2.2 (polyreactions in bulk), 2.2.3 (polyreactions in solution), and 2.2.4 (polyreactions in dispersion). Prior to this some special features... 

In heterogeneous polymerizations in bulk, the formed polymer is insoluble in its monomer and the polyreaction is performed below the softening point of the polymer. On an industrial scale, this type of process is especially utilized for chain polymerizations, for example, the radical polymerization of liquid vinyl chloride, the polymerization of liquid propylene with Ziegler-Natta or with metallocene catalysts, and the polymerization of molten trioxane. 

There are two different ways for carrying out polyreactions in a solvent. When both the monomer and the resulting polymer are soluble in the solvent, one speaks of a homogeneous solution polymerization on the other hand, if the polymer precipitates during the course of the reaction, it is called precipitation polymerization. By addition of a solvent, different effects are obtained Basically, the viscosity of the reaction mixture is decreased in comparison to a bulk polyreaction this facilitates heat transfer, mass transport, and handling. 

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