Removal of volatile organic compounds from paper coatings

From the chemical point of view paper coatings are mainly polymer dispersions. Polymer dispersions are constituted in multitude fields, for example as dispersion coatings or adhesives. As far as no additional treatment is done, polymer materials as well as polymer agents contain non polymer, volatile organic components that may arise from: (1) incomplete polymerization of the applied monomers, (2) primary materials containing non polymerizable components, (3) undesirable side reactions during the synthesis. Requirements for the removal of volatile substances from polymer dispersion are given by several reasons: (1) low molecular substances deteriorate the product characteristics (viscosity, thermal stability and others), (2) in order to comply with legislative standards, volatile organic compounds have to be removed from dispersions, especially when applied to large surfaces (e.g. in surface refining in paper and leather industries as well as on coating). The removal of volatile organic compounds (deodorization) can be realized in continuous or discontinuous processes. In contrast to highly developed process technology, the process itself is not well understood, especially mass transport phenomena between the gas phase and the aqueous polymer dispersion are insufficiently and controversially discussed in the literature. Two processes, their advantages and disadvantages and the description by mathematical- mechanistic models are presented in this paper.