Aqueous Dispersion Coating Chemistry Optimization for High Yield Mechanical Hydrapulping
Optimizing carboxylated acrylic dispersion coatings enables complete mechanical pulp fiber liberation while keeping screen rejects below one percent.
Macro-Stickies Formation
Adhesive Aggregation
Agglomerated particles of synthetic polymers originating from pressure sensitive tapes or label backings accumulate within a pulp slurry when recycled paper stock undergoes secondary processing. The macro-stickies formation reduces the functional integrity of paper webs by creating spots that interfere with printing surfaces or cause picking during high speed converting operations. Filtration cycles separate these contaminants through screens with specific slot widths designed to capture particles exceeding a hundred micrometers in diameter.
Material Mechanism
Secondary fibres contain hydrophobic components that refuse to disperse into an aqueous suspension. These substances collide during the agitation phase of repulping and coalesce into larger, tacky masses. Thermal fluctuations during dispersion stages increase the viscosity of the adhesive fractions, which encourages the buildup of larger particles if cooling occurs too rapidly.
Centrifugal cleaners exert physical forces that separate these entities from the denser fibre mass based on differing specific gravities.
Quality Threshold
Manufacturers measure the concentration of these contaminants by counting the number of visible spots per square meter of finished paper product. High levels of these deposits force printers to halt production runs to clean blankets or plates as the tacky material adheres to the cylinders. Standard industrial practice demands the removal of these particles to levels that do not compromise the strength or surface uniformity of thin packaging stocks.
Final sheets with excessive contamination fail to meet the performance requirements for coating applications where a clean finish remains a requirement.