Wet End Process
Industrial chemistry system functions at the wet end of a paper machine to ensure that small fibres and mineral fillers remain within the forming web. Effective retention chemistry improves the efficiency of the production line by reducing the solids load in the white water system. It defines the physical stability of the sheet during the rapid drainage of water on the fourdrinier table.
Flocculation Strategy
Cationic polymers are added to the pulp slurry to neutralize the negative charges on the surface of the cellulose fibres and mineral fillers. This charge neutralisation allows the particles to come together into larger clumps called flocs which are easily trapped by the mat of longer fibres. Microparticles or silica are often introduced later in the sequence to tighten these flocs and increase the drainage speed without losing the fine materials.
Process Outcome
Proper management of these additives leads to a more uniform sheet with consistent opacity and weight. High retention rates reduce the amount of expensive titanium dioxide or calcium carbonate that a mill must purchase to meet brightness targets. If the chemistry is out of balance the machine suffers from deposits and increased wear on the forming fabrics.
