Dynamic Contact Angle Relaxation Kinetics in High Speed Blade Coating Systems
Dynamic contact angle relaxation rates dictate air entrainment and streak defect thresholds in high speed blade coating systems operating above 1200 m/min.
Coat Weight Deposition
Application Rate
Quantitative measurement of the dry mass of coating material applied to a unit area of a paper or board surface. Coat weight deposition determines the final opacity and ink receptivity of the substrate. It is expressed in grams per square meter.
Control Mechanism
Blade coaters and air knives regulate the amount of liquid slurry remaining on the base sheet. A metered film transfer press provides an alternative method by pre-measuring the coating before it touches the paper. Variations in the base sheet porosity or the viscosity of the coating mix alter the final result.
If the coat weight deposition is too high, the surface may suffer from picking or cracking during folding. Low deposition leads to insufficient coverage and poor image reproduction.
Performance Constraint
Balance between cost and surface performance dictates the target level for a specific grade. High coat weight deposition improves the brightness and gloss of the sheet but increases the total weight and cost of the material. Converters monitor this value to predict how the board will behave on a high speed printing press.
Consistent application prevents the mottle and streaking that occur when the coating layer is uneven. Adjustments to the coating formulation often occur at the mill to compensate for changes in base paper moisture or temperature.