Application of Pre-mixed Complexes as Flocculants

Onabe [84] analyzed the drainage behavior of pulp suspensions with a two-component system, with attention to polyion complex formation. With cationic and anionic polyacrylamides (molecular weights 3,000,000 and 1,000,000 g/mol) added individually, a polyion complex with an irregular three-dimensional stmcmre was precipitated on the fiber surface. This reduced the homogeneity of the paper sheets. In contrast to this, a pre-mixed system of an anionic and cationic polyacrylamide [83] resulted in an improvement in pulp retention and paper quality (paper strength). Because of the very high molar mass and thus the big coil diameter, the formed PECs are very big and are therefore good flocculants. 

CMC-rich cellulose sheets were prepared by Uematsu [86] with a cationic retention aid. When 5% poly(NAW-trimethyl-N-(2-methacryloxyethyl) ammonium 

PEC dispersions have been used as a fixing agent, flocculant, or retention aid to increase the water resistance of paper [87]. 

Detailed studies of particle (silica) flocculation using pre-mixed complexes were done by Buchhammer [88], Schwarz and Dragan [89], and Mende et al. [90, 91]. 

The flocculation efficiency of some nonstoichiometric interpolyelectrolyte complex dispersions synthesized by the interaction between poly(sodium 2-acrylamido-2-methylpropanesulfonate) (NaPAMPS) and three strong PCs bearing quaternary ammonium salt centers in the backbone on a stable monodisperse silica dispersion have been tested. The PCs PDADMAC and PCA5 alone showed a very narrow range of flocculation. In the case of the most hydrophobic PC, PCA5D1, the window of optimum flocculation concentration was broader compared with other PCs [88]. 

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