Paperboard Wet End Additive Sorption Mechanics and Chemical Retention Verification
Verify paperboard wet end additive retention using dynamic drainage jars and extraction GC-MS to ensure food contact compliance and prevent converting failures.
Microparticle Retention
Colloidal Aggregation
The attachment of fine fibers, mineral fillers, and sizing agents to the forming paper web is controlled by adding high molecular weight polymers followed by highly charged inorganic particles. This chemical strategy, termed microparticle retention, improves sheet uniformity while maintaining high drainage rates on the forming wire. It ensures that valuable papermaking materials remain in the sheet rather than being lost to the white water system.
Floc Structure
The mechanism relies on the formation of dense, shear-resistant flocs when cationic polyacrylamide is added followed by anionic silica or bentonite. These inorganic microparticles act as multi-functional cross-linkers that contract the pre-existing polymer bridges. This action produces small, tightly bound fiber-filler aggregates that do not disrupt sheet formation.
Dewatering Kinetics
Accelerated water removal on the forming wire is a major operational benefit of this microparticle system. By grouping the fines and fillers into tight aggregates, the porosity of the fiber mat remains open, which permits rapid water escape. This increased drainage rate allows the paper machine to run at higher speeds while reducing the vacuum energy needed in the suction boxes.
It also ensures a drier sheet enters the press section, which decreases the steam required in the drying section.