Polyethyleneimine was found to be combined with partially hydrolyzed polyacrylamide in aqueous solution to give a high molecular complex compound. The complex compound having many imino and carboxylate groups indicated the properties of amphoteric polyelectrolyte. The cationic and anionic properties of the complex compound were found to depend upon the combining ratio, molecular weight and hydrolyzing degree of the components and hydrogen ion concentration of the solution.
Each obtainable compound came to present higher anionic properties in proportion to the hydrolyzing degree of polyacrylamide, or oin inverse proportion to the mixing ratio of polyethyleneimine and the hydrogen ion concentration of its solution : while it shew as much cationic properties, providing these constitutent ratios counterwork. Balancing of the strength of both cationic and anionic groups in the compound minimized the solubility of the compound and the solution of certain concentration became turbid by precipitation. The turbid solution could recover the former clearity by adding acid or alkali into the solution or by heating.
It was found that the complex polyelectolyte is a very excellent flocculating agent. The flocculating capability was far superior to that of polyethyleneimine or polyacrylamide alone, because the polyelectrolyte has very high molecular weight and enormous number of ionic groups. In suspension of clay or fine pulp fibers, for example, the complex compound adsorbed readily at the surface of the suspending particles of every sizes, and flocculation occured through decreasing of zeta potential of particles and interparticle bridging by macromolecular chains.
In paper making, the addition of the complex polyelectrolyte into pulp suspension in beating process gave excellent effect on sizing and strength of the paper made up. The application of the compound was effective even in the paper making in which aluminium sulfate is limited to use. The flocculating effect was also found to utilize to clarify white water that is waste water in paper making industry.
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