Sizing agents for wet end and surface application

Sizing agents, belonging to the group of functional chemicals, represent the second largest group after the coating binder of specialty chemicals for the paper manufacturing. Rosin size, Alkylketendimer(AKD), Alkenylsuccinicanhydride (ASA) and Polymeric Sizing Agents (PSA) are the main representatives of that group. The aim of this paper is to wrap up the information of preceding articles published in this serie supplemented with newer insights and to give an overview of the fate and behaviour of sizing agents in the environment. Rosin size, AKD and ASA are traditionally added to the wet end, which subsequently results in an product retention which is strongly dependent on the wire retention of the Paper Machine. Solely PSA which was developed ad hoc for the purpose of surface treatment is retained quantitatively with the produced paper The continuance of wet end sizing agents in paper vary under compliance with technical parameters between 70 to 90 % and thus result in an ecologically reasonable and gentle utilisaztion of resources Sometimes the yield is deliberately much lower also sometimes it happens to be much lower unbeknownst to somebody. The life cycle assessment depends for AKD and ASA strongly on the effective use and a low level of undesired interactions. The common understanding that AKD and ASA were known as low respectively not biodegradeable has changend recently. Newest investigation on AKD showed that this substance is biodegradeable when tested under application relevant conditions. Subsequently the former labeling for this product class could be abolished. To what extend this correlates with A SA is so far not experimentally proven under OECD relevant conditions but from the chemical constitution it can be concluded by analogy that it should even be better biologically disposable. For all wet end sizing agents the destination in the effluent show values below 1 %, in the case of surface sizing agents a changeover to the effluent is negligible and product residues leave the Mill only attached on solid material.