Alkyl Ketene Dimer Wet End Hydrolysis in Alkaline Hardwood Furnish
Alkyl ketene dimer hydrolysis in alkaline hardwood stock converts active sizing wax into unreactive dialkyl ketone, raising chemical costs and felt deposits.
Hydrophobic Wax Deposits
Deposition Mechanism
Secondary stickies and organic agglomerates in recycled fibre repulping streams represent insoluble tacky compounds that destabilize wet-end chemistry. Uncoated packaging grades processed from old corrugated containers frequently carry hydrophobic wax deposits into the stock chest when repulping temperatures exceed the melting point of petroleum-based board coatings. These tacky particles agglomerate under mechanical shear and adhere to wire strands, press felts, dryer fabrics and drying cylinders.
Phase separation occurs as dissolved paraffin or microcrystalline wax cools below its thermal softening threshold. Agglomeration accelerates when calcium ions interact with carboxylated surfactants on the wax surface.
Papermaking Consequence
Sheet holes and localized picking on calender stacks result directly from tacky surface accumulation. When hydrophobic wax deposits transfer onto the paper web, local surface energy drops, preventing uniform starch absorption during size press application. This localized barrier causes pinhole defects and print repulsiveness during flexographic ink transfer.
Operational Boundary
Chemical passivating agents such as talc or non-ionic dispersants stabilize low concentrations of paraffin in stock suspensions. When thermal fluctuations cross thirty-five degrees Celsius or furnish wax content exceeds zero point two percent by dry weight, chemical passivating agents fail to prevent agglomeration. Modern mechanical screening removes discrete wax flakes at low temperatures, but fine emulsion droplets pass through screen baskets and deposit on machine clothing downstream.