Mechanisms of Filler Flocculation with PEO/Cofactor Dual-component Flocculants

Abstract

<p>High molecular weight poly(ethylene oxide) (PEO) is used in papermaking as a flocculant to incorporate fines and fillers into papers. PEO flocculation is more effective in the presence of cofactors, which are phenolic polymers capable of forming aqueous complexes with PEO. In this work, two types of model cofactors were developed to study the PEO/cofactor flocculation mechanism. The first type of cofactors were latex particles with polystyrene-core poly(vinyl phenol)-shell (PS-PVPh) prepared by the surfactant-free emulsion polymerization. It was found that PS-PVPh particles enhanced the ability of PEO to flocculate polystyrene latex. When composite particles were added after PEO, they bridged together PEO-coated particles and aggregates. When composite particles were added after PEO, they bridged together PEO-coated particles and aggregates. When composite particles were added before PEO, they acted as bridging agents and adsorb PEO in an extended configuration ideal for flocculation.</p> <p>The second type of cofactors developed were water soluble tyrosine-containing polypeptides (TCP). TCP cofactors had well-defined structures and were optically active. Therefore, many analytical techniques, such as NMR, light scattering, isothermal titration calorimetry, and circular dichroism, were able to be applied to study the PEO/TCP complex formation mechanism. By taking into account the complex formation mechanism, the complex bridging flocculation mechanism of Xiao et al. was extended to explain many flocculation mechanisms. According to the extended mecahnism, PEO/TCP complexes function as bridges to couple filler particles. Meanwhile, the complexes undergo deactivation - this is a new concept developed in this work. The deactivated complexes lose the ability to couple fillers, preventing the flocculation from reaching completion. It was proposed that the deactivation was induced by the encapsulation of TCP phenolic groups by PEO.</p>