Paperboard Converting Mass Balance Accounting and Scrap Yield Baselines
Paperboard mass balance accounting requires deducting real converting process scrap and moisture variations from credit ledgers to prevent invalid claims.
Volatile Evaporation Loss Converting
Mass Reduction
Solvent and water vaporization during liquid coating application reduces the applied wet film mass to its final dry coating weight. In web converting processes, volatile evaporation loss converting accounts for the mass difference between liquid wet ink or adhesive applied to paperboard and the cured solid deposit remaining on the substrate. The process determines real-time dryer thermal energy requirements and solid coating yield.
Drying Mechanism
Liquid coatings consist of solid resins and functional additives suspended inside volatile solvents or water. Passing the coated paperboard web through flotation dryers drives off volatile carrier fluids through convective heat transfer. A gravure coater applying twenty grams per square metre of wet coating at thirty percent solids leaves six grams per square metre of dry coat weight, resulting in fourteen grams per square metre of volatile loss.
Monitoring exhaust vapor concentration prevents solvent buildup from reaching lower explosive limits inside drying hoods. Accurate calculation of flash-off loss maintains precise dried film thickness control without over-drying the underlying paperboard substrate.
Process Control
Incomplete solvent removal leaves residual volatile compounds that cause coating tackiness and carton blocking. Over-drying removes structural moisture from paperboard, causing sheet curl and embrittlement. Continuous measurement of mass loss maintains correct dryer balance during high-speed converting runs.