Comparing the fiber flocculation behavior of several wet-end retention systems.

APPLICATION: By choosing the appropriate retention system, papermakers can strike the best balance between costs and fiber flocculation.

Are some retention systems more detrimental to sheet formation than others? Many retention aids increase the tendency of fibers to flocculate, which can cause uneven sheet formation. In comparing how well retention aids perform, part of the evaluation hinges on optimizing the balance between retention and flocculation.

In experiments carried out with representative furnishes in a pilot-scale flow loop, the researchers compared five retention systems in terms of operating costs, drainage, and the balance between flocculation and filler retention. Fiber flocculation was evaluated with an image analysis technique that is not sensitive to the presence of filler. Experimental models were used to optimize the retention performance of each system with regard to its effects on flocculation.

The five systems showed different responses to fiber flocculation. One microparticle system, ATC + CS + ASI, showed the lowest sensitivity to fiber flocculation, but it was the system with the highest cost. A polyelectrolyte system, ATC + CS + APAM, appeared to be the most cost effective, but the operating cost doubles when conditions are optimized to improve drainage. View this paper online at http://www.tappi.org/index.asp?pid=29099

Patrick Huber, Christian Pierre, Christian Bermond, and Bruno Carre are with the Centre Technique du Papier, BP 251, 38044 Grenoble, France. Email Huber at [e-mail]