NOVEL RETENTION AIDS FOR MECHANICAL PULPS

Acrylamide and poly(ethylene glycol) macromonomer copolymers, in conju nction with phenolic formaldehyde resin (PFR), were evaluated as novel retention aids for newsprint pulps. The first-pass retention of the p ulp fines was increased from 37% without polymer to nearly 90% with co polymer addition. This retention performance was similar to that of th e high molecular weight poly(ethylene oxide) (PEO)/phenolic resin dual -polymer systems. However, the copolymers exhibited improved aging res istance and produced a higher fines retention than PEO (MW = 8 million ) under high shear stress. The retention performance of the copolymers was very sensitive to the molecular weight. A new retention mechanism called complex bridging was proposed to explain the retention effects . Application: This work deals with a new copolymer that newsprint pro ducers may be able to use to improve first-pass retention.