Mineral Coating Pigment Packing Micro Geometry and Pore Volume Distribution
Pigment micro-geometry and particle packing dictate coat pore volume distribution, controlling ink vehicle absorption rate, print gloss, and coat strength.
Dewatering Filtration Rate
Drainage Velocity
Volumetric speed at which water is separated from a dilute suspension of cellulose fibres during the sheet-forming process. In paper and paperboard manufacturing, the dewatering filtration rate determines how quickly the wet web can dry on the forming fabric. This physical property directly influences the maximum running speed of the paper machine.
Process Variable
Chemical drainage aids and retention polymers are added to the pulp slurry to agglomerate fine particles and improve water release without causing sheet non-uniformity. The structure of the forming wire, the vacuum applied beneath the wire, and the temperature of the stock also govern the rate of water removal. As temperature rises, the viscosity of water decreases, which accelerates the drainage process.
If the dewatering filtration rate is too low, the wet web enters the press section with excess moisture, which leads to web breaks and increased steam consumption in the drying cylinders.
Operational Impact
Monitoring the drainage speed helps operators optimize the dosage of chemical additives and adjust machine speed to match the drying capacity of the system. This optimization prevents defects like crushing or blistering in the paperboard. Stable water removal ensures a uniform basis weight across the entire width of the machine.