Barrier Paperboard Substrate Selection and Wet End Disintegration Yield Testing
Aqueous dispersion barrier boards outperform extruded polyolefins by delivering over 95 percent wet end fiber yield and avoiding heavy EPR penalties.
Alkaline Repulping
Chemical Suspension
Paper recycling relies on the systematic breakdown of recovered fibres through aqueous agitation at elevated pH levels. Alkaline repulping utilizes sodium hydroxide or sodium carbonate to swell cellulose, which facilitates the detachment of inks, coatings, and binders from the stock. This process governs the release of contaminants by increasing the surface charge of fibre bundles to prevent redeposition.
Operations maintain a pH range between eight and eleven to balance fibre strength preservation with the efficacy of chemical detachment.
Process Mechanism
Caustic soda introduction triggers the saponification of fatty acid binders found in offset lithographic inks. Water temperature typically ranges between forty and sixty degrees Celsius to accelerate the diffusion of these reagents into the dense structure of compacted paper bales. Mechanical shear forces then act upon the softened material to generate a homogenous slurry.
High consistency pulpers operate at concentrations exceeding fifteen percent solids to maximize the rubbing action between individual fibre segments.
Contaminant Removal
Flotation cells depend on the successful implementation of this chemistry to achieve high brightness levels in final recycled sheets. Air bubbles carry the detached hydrophobic particles to the surface of the tank, where specialized scrapers remove the collected sludge. Minimal residual chemical carryover protects downstream bleaching agents from premature neutralization and ensures the stability of final pH values.
Proper adherence to these chemical concentrations dictates the overall efficiency of secondary fibre recovery.