The role of vapour deposition in the hydrophobization treatment of cellulose fibres using alkyl ketene dimers and alkenyl succinic acid anhydrides

The possibility of delivering hydrophobization (or sizing) effect to cellulose fibre via AKD and ASA vapours was investigated using a novel method. Alkyl ketene dimer (AKD) and alkenyl succinic acid anhydride (ASA) are two of widely used hydrophobization chemicals in papermaking industry. It has been reported that sizing effect could be delivered by the vapourization and re-deposition mechanism under papermaking condition. Such a conclusion was reached in previous studies by measuring the level of hydrophobicity acquired by cellulose or glass surface after being exposed to the vapours of these AKD or ASA. In this work we investigated the possibility of vapour sizing by analyzing the chemical compositions of the vapours of AKD and ASA at typical papermaking temperatures. Our results suggest that the vapour of ASA has the same composition as the ASA liquid. However, the vapour of AKD is dominated by fatty acids (which are the initial materials for AKD synthesis). The actual AKD concentration in the vapour phase is below the detection limit of FTIR. These results indicate that cellulose hydrophobization via vapour is possible with ASA, but not practically possible for AKD.