Reactive paper sizing agents, such as alkenyl succinic anhydride (ASA), provide hydrophobicity to paper. The reactive anhydride group of these reagents is highly susceptible to reaction with water and thus resistance against hydrolysis is of primary importance for their practical application. This study describes different application-relevant properties of recently developed sizing agents that are based on renewable vegetable oils including hydrolysis behavior, time-dependent sizing efficiency, and tendency to form deposits or foam. The novel sizing agents - maleated high oleic sunflower oil (MSOHO) and maleated rapeseed oil (MRSO) - are compared to conventional ASA as the state-of-the-art sizing agent. Although the reactive group is the same in all reagents, there are pronounced differences between the three reagents, with MSOHO showing the best performance, i.e., the slowest hydrolysis. This oil has a higher ratio of hydrophobic side chains that impede the water attack at the anhydride group. Also, the higher viscosity of MSOHO plays an important role in performance, because diffusion of water molecules into a MSOHO emulsion droplet is much slower than in the case of conventional ASA.
