Energy curve of homopolymerisation

The main concern for safety is the control of the reaction temperature and of oxygen due to the exothermic nature of the process and the resulting danger of a runaway reaction. The rate of polymerisation increases with temperature while the rate of heat transfer decreases with increasing conversion due to increased viscosity. An effective process control is essential for keeping the reaction under control. 

Residual monomers constitute one of the major by-products at the end of the reaction. They are usually not emitted but either separated or returned into the process in a closed loop or sent to a separate treatment unit or burnt, if possible with energy recovery. Residual monomers may also be dissolved in the final product. The reduction to legally specified or lower levels requires additional treatment during the work-up phase. 

Auxiliaries sueh as initiators, ehain transfer agents or sometimes emulsifiers or colloidal stabilisers either become part of the product or are separated. 

Some of the monomers, dispersants and additives used can be dangerous for human health and/or the environment, and available information on the reduction of their emissions or their substitution has to be taken into aecount when selecting BAT [27, TWGComments, 2004]. 

Polymerisation reactors tend to build up solid layers of product along die inside walls of the reactor or the heat exehangers after extended periods of running. The exact conditions for this unwanted side-effeet are different for each monomer and each process. This layer will interfere with the necessary removal of heat and may cause product impurities resulting, for instance, in so-called fish eyes in film applieations. Therefore, it is removed from time to time. The necessary opening of the reactor may cause emissions of unreacted monomers and/or solvents. 

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