Rosin sizes anionic trash

If pre-treatment is not possible, then the only solution is to remove the rosin/alum reaction as far from the anionic trash as possible, i.e. pre-mix sizing or CRS, and reduce the contact time by late addition of size and alum. This, however, will not cure the problem completely, as the high surface area effect will still be present. 

There are some components which may be regarded as anionic trash that are beneficial to rosin sizing such as saccharinic acids from alkaline pulping and hemicelluloses from unbleached pulps. These can form complexes with AP+ ions and produce rosin size precipitates of lower melting or sintering points. This promotes more efficient sizing. 

An example of problems occurring from anionic trash, of which there are many, is a board mill using a mixed waste furnish. In this mill, waste was not well sorted and was loaded into a pulper in proportions depending on whether it was KLS or white. On a certain grade of board it was found to be almost impossible to obtain the sizing required. A threefold increase in rosin size and a twofold increase in alum were needed to obtain the sizing degree required. 

Anionic trash, in synthetic sizing, has a similar effect on size retention as that for rosin size, except that in this case, it is the size that carries the cationic charge, not the alum. This will mean that it is the sizing agent that will be adsorbed onto the anionic trash. If the size is adsorbed onto the anionic trash, sizing will be subject to the retention of this anionic trash and will vary accordingly. This is why mnch more emphasis is placed on the correct retention system to improve anionic trash retention, or fmes/filler retention, as much of the size can also be adsorbed on this. 

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