INTEGRATING THE FILLER WITH THE RETENTION AID - AN EXAMPLE OF THE OPTIMIZED USE OF CHEMICALS IN PAPERMAKING

Because of the continuing trend towards neutral papermaking and the ever increasing closure of paper mill white water systems, more importance is being attached to the discriminating use of chemicals in the papermaking process. The decisive factors here are that the process chemicals are tailored to the applications for which they are used, and that the best points of addition are chosen. Nowadays, fillers are mostly added to the furnish in the form of highly concentrated, low-viscosity suspensions. They contain polyanionic dispersing agents which have a detrimental effect on the papermaking process. Special, modified polyethylenimines make it possible to prepare cationic calcium carbonate suspensions with a concentration of 70%. They also have the effect of fixing the calcium carbonate to the fibres. Integrating the retention aid with the filler results in high first-pass retention, which can be boosted even further by adding high-molar-mass anionic retention aids. The result is that calcium carbonate content in the headbox is low and the calcium carbonate is evenly distributed in the paper, which is of great benefit to papermakers.