Mechanism of polyacrylamide-bentonite - microparticulate retention aids

The use of microparticulate retention aids was investigated in three differ ent papermaking systems: the deposition of PCC on kraft fibers, flocculatio n of TMP fibers and the deposition of fines on TMP fibers. It is shown that montmorillonite significantly increases both particle deposition and fiber flocculation. This is attributed to a higher bond strength in the presence of a microparticle. The role of the microparticles is to provide links bet ween adsorbed polymer layers. The bond strengthening is explained by the as ymmetric nature of an adsorbed polymer layer.