Rosin sizes drying temperature

The ideal drying conditions for ASA and rosin sizing differ from those of AKD, whereas for ASA and rosin there should be mild drying in the early drying section, AKD benefits from more extreme temperatures. 

As stated for rosin size, the drying temperature is important for synthetic sizes, but the profile is more important and as long as a profile similar to that of the ideal is used, lack of sizing should not be a problem. However, it is a case of trial and error to obtain the correct dryer profile for individual machines, to obtain the best balance of sizing performance and energy input. 

AKDs are waxy, water-insoluble solids with melting points around 50 °C, and ASAs are viscous water-insoluble liquids at room temperature. It is necessary to prepare them as stabilised emulsions by dispersion in a cationic polymer (normally cationic starch). Small amounts of retention aid and surfactants may also be present. Particle size distributions are around 1 fim, and addition levels around 0.1% (of pure AKD or ASA) by weight of dry fibre. This is an order of magnitude lower than the amount of rosin used in rosin-alum sizing (1-2%). Emulsions of AKD are more hydrolytically stable than ASA, and the latter must be emulsified on-site and used within a few hours. 

As has been previously explained, this differs for soap and dispersed sizes (anionic, or cationic), as soap size precipitates are almost entirely aluminium rosinate, which must have the correct moisture and temperature before sintering takes place, whereas dispersed sizes contain high levels of free rosin, which can melt redistribute and react with aluminium species under normal drying conditions. 

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