Retention mechanisms for two-component systems based on phenolic resins and PEO or new PEO-copolymer retention aids

Retention aids based on novel copolymers of acrylamide and polyethylene glycol macromonomer, as well as high molecular weight poly(ethylene oxide) (PRO), are believed to function by a mechanism we have called "complex bridging flocculation". According to this mechanism, PEO molecules aggregate in the presence of phenol formaldehyde resin (PFR) to form a colloidally dispersed polymer complex which heteroflocculates with the latex particles. Complex bridging explained both published data and new experimental observations. A well-known observation is that extremely high (i.e. >2×10⁶) molecular PEO is required for good flocculation. It is proposed that the PEO/PFR complex collapses to an inactive (with respect to flocculation) coacervate, and only with very high molecular weight PEO does this collapse occur slowly enough for flocculation to occur.