Flexible Packaging

Flexible packaging has been almost entirely solvent-based since its inception, because toluene, ethyl acetate and alcohol blends dry fast, wet polyolefin films and give the resolubility that gravure’s open cells need. Water changes every one of those properties, and the four barriers — drying, wetting, resolubility and lamination bond — define the work.

Water has a latent heat of evaporation roughly five times that of ethyl acetate and a surface tension of 72 mN/m against 24. We answer the first with solids of 40–50 % against 25–35 % for solvent inks, cells engraved 15–25 % shallower, and high-velocity impingement drying at 70–90 °C. We answer the second with surfactant and co-solvent packages that bring surface tension down to about 30 mN/m, plus corona treatment to 40–42 mN/m in line.