Anionic trash catchers

The number of chemicals used to maintain the balance on the paper machine of both process chemicals, e.g. three or four component retention aids, deposit control chemicals as well as defoamers and anionic trash catchers (ATC) and performance chemicals, e.g. cationic starch, size, filler and perhaps wet strength resin and/or dye, has resulted in a wet-end soup . 

Anionic colloids may complex with cationic starch, reducing the ability of the starch to bond to the fibre surface. Hydrocolloid complexes may also be formed, resulting in poor de-watering and pressing efficiencies. Disturbing anionic trash should be neutralised with a suitable anionic trash catcher before addition of cationic starch to the system. This topic is well covered in several woiks by Pieter Brower [22-27]. 

Anionic trash catchers are either inorganic salts (aluminium, zirconium) or high charged cationic polymers. Extranely high DS, low molecular weight cationic starches are available for use in this application and are found to quench OBAs much less than polymers such as poly-DADMAC or polyacrylamide. 

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