Heat Sealability and Water Vapor Permeability of Barrier Dispersion Coatings, 2002 Coating Conference Proceedings

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The heat sealability of barrier-coated paper has been investigated for a series of latex dispersions, some of which were carboxylated and some not. The influence of the neutralizing agents NH3 and NaOH has also been studied. The dispersions were applied onto a three-ply base paper by using a pilot metering size press coater. The effect of drying was investigated by applying either low or intense IR-power.

Blocking is known to be a serious problem with barrier dispersions, and the relationship between blocking tendency of coated material (subjective ranking of separation resistance) and other investigated parameters was therefore studied in some detail. Two parameters were considered: surface roughness and the presence of contaminants.

The water vapor permeability of the coated material was analyzed by the gravimetric cup method. Heat sealability was evaluated by measurement of Y-peel force on sealed material and the results were interpreted with the support of SEM and ESCA analyses.

The results showed that carboxylation has a favorable effect on both barrier properties and heat sealability. The presence of surfactant on the coating surface was shown to give poor adhesion between sealing surfaces. Removal of the surfactant layer by rinsing shifted the locus of failure to the base sheet, indicating the formation of a stronger seal.