The redistribution of alkyl ketene dimers (AKD) on a fibre surface after sizing plays an important role in the sizing of paper. A good coverage of AKD on a fibre surface is a prerequisite for achieving a good sizing effect. It is a common observation that ketone (hydrolysed AKD) does not provide the same level of sizing as AKD under the same sizing conditions, despite the fact that ketone is more hydrophobic than AKD. This has generally been thought to be due to the inability of ketone to form a β-ketoester bond with cellulose. Recent work in our laboratory has focused on comparing the spreading of AKD and ketone on glass, silicon wafer and regenerated cellulose surfaces (models chosen for cellulose fibres as they possess OH groups). In the present study the weak sizing ability of ketone was investigated by examining the spreading behaviour of AKD and the corresponding ketone. The focus was on the effect of the melting of AKD, and the corresponding ketones and mixtures of AKD and ketones, on their spreading behaviour. The results show that the melting point of the AKD wax (∼53°C) is markedly lower than that of the corresponding ketone wax (∼79°C). Furthermore, AKD and ketone waxes do not form a totally miscible binary system. The much higher melting point of the latter has a strong negative impact on its spreading ability and this may be one of the factors contributing to poorer sizing performance of ketone compared with AKD. Some indirect results obtained from glass surfaces suggest that ketone has a potential to provide a good level of sizing to glass surfaces, if a good surface coverage of ketone can be achieved. However, to understand the weak sizing ability of ketone to cellulose, further studies using ideal cellulose substrates must be conducted.
|Number of pages||7|
|Publication status||Published - 1 Sep 2002|
- Melting points
- Spreading rates