Effects of Deinking Chemicals on Sticky Depositions, 2000 Recycling Symposium Proceedings

Thomas Krauthauf, Hans Joachim Putz, Lothar Göttsching--In order to find solutions for the manifold problems created by stickies in papermaking, a comprehensive knowledge of the fundamentals of sticky deposition has to be developed. For this reason a survey has been conducted that takes into account different sticky sources and several parameters for defined pulp systems. A prerequisite for such a survey has to be a meaningful method to simulate sticky deposition including deposition of micro stickies under laboratory conditions. In trials with pressure sensitive adhesives (PSAs) as sticky sources, the new INGEDE FAC-Analyzer has shown good sticky recovery rates with low error rates. It was also shown that, with this analyzer, there are no limitations in respect to the particle sizes of deposits which include micro stickies. The trials have been conducted with uncoated paper and paper that was coated in a pilot plant coater with three different coating compositions and printed under constant conditions in a rotogravure press. The coatings differed only in the binder. All other parameters have been kept constant. The commercial binders included acrylate, polyvinylacetate and polystyrol. In addition to the binders, dispersion PSA was used as potential sticky source (2-ethyl-hexyl acrylates). The PSA was added both as the original dispersion as well as after its application on labels. The papers with or without adhesive were pulped with different compositions of deinking chemicals. The results show significant changes of the deposition behavior of the coating binders. Especially the deinking chemicals have an impact on the deposition results though these effects are mostly reversible by flotation.