Aqueous Glue Setting in Double-Coated Paperboard Systems: The Impact of Application System and Individual Coating Layer Thickness on Glue Bond Formation, 2011 PaperCon Conference

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In this study, pilot-scale coating trials have been designed and carried out in order to investigate the roles of both the coating application/metering technique and the contribution of individual layer thickness on the bond formation of aqueous glues in double-coated paperboard systems. The coating application systems investigated for the basecoat and topcoat layers comprised the following: Rod/Rod, Rod/Air-Knife, Blade/Air-Knife, Blade/Blade and Film Coater/Air-Knife. The impact of basecoat and topcoat layer thickness was investigated by modifying the two-layer structure as follows: HIGH/LOW, MEDIUM/MEDIUM, LOW/HIGH for each of the above mentioned application systems, whilst maintaining a constant total coat weight.

In addition to standard glue strength testing, an attempt was made to quantify the extent of aqueous glue penetration into the coating layers using both optical and electron microscopy techniques utilizing tracers in the glue. The surface roughness, bulk porosity, and absorption potential of the coating layers were found to be dependent on the application technique; however the impact of individual layer thickness was not observed to be a contributing factor in predicting end-use performance. The use of Laser Scanning Confocal Microscopy with a Rhodamine-B dye in the glue produced the best results for observing the extent of penetration into the coating layers.