MODELING OF MASS-TRANSFER OF VOLATILE ORGANIC-COMPOUNDS IN POLYMER DISPERSIONS

Polymers may contain low molecular organic components due to incomplet e conversion, contaminated raw materials and/or undesirable side react ions. Aqueous polymer solutions, e.g. dispersion paints, adhesives or refining media in the paper industry, are usually applied to large sur faces. During this operation, low molecular weight components are emit ted into the ambient air if not removed before. While existing removal processes operate fairly well, the mass transfer steps are still poor ly understood and therefore there are no designing data which can be c laimed to be reliable. Here a mechanistical mathematical model is pres ented which accounts for the crucial mass transfer steps occurring in a stationary continuous, well. mixed stripping apparatus. Phase equili bria and attainable monomer removal have been determined experimentall y in an aerosol jet loop reactor. The results indicate that an efficie nt stripping process essentially depends on distribution coefficients, hydrodynamic properties and operating conditions while diffusion insi de the latices is negligible. This is true for operating temperatures higher than the polymer glass temperature. These results are in contra diction to statements of some other authors who consider diffusion ins ide the latex particle as the limiting step. (C) 1997 Elsevier Science S.A.