Influence of formulation and properties of water-based flexographic inks on printing performance for PE-coated board

In this study the flexographic printing of low-density polyethylene- (LDPE-) coated liquid packaging board is analysed for a range of water-based inks, varying in type of pigment and acrylate-polymer vehicle and pigment/vehicle mixing proportions. One vehicle is solely based on emulsion polymer, another contains solution polymer, and the third is a 50/50 blend of these two. Vehicle type and relative amount are shown to have a strong and systematic bearing on the absolute amount of ink transferred and its corresponding print density, gloss, and uniformity. For both ink colours (cyan and black), transferred amount increases with pigment content and is highest for the 50/50 intermediate vehicle. Print density and homogeneity are generally highest for the vehicle containing highest content of solution polymer, at least with the lower anilox volumes, and this vehicle also gives highest print gloss. The wet amount of ink transferred is shown to be well correlated to its surface tension and viscosity.