Water-Based Technology

Water has a latent heat of evaporation of 2260 kJ/kg, roughly five times that of ethyl acetate, and a surface tension of 72 mN/m against 24 for the solvent. The first fact means the dryer must deliver five times the energy per kilogram of carrier; the second means the ink will not wet a polyolefin film at 38–42 mN/m without help.

Binder. Our water-based inks are built on a blend of alkali-soluble acrylic resin, which gives resolubility on the anilox and plate plus gloss and pigment wetting, and acrylic emulsion polymer, which gives rub and water resistance once the amine has left the film. The ratio is set per grade: more resin for high-gloss wrap and long runs, more emulsion for bags and cups handled wet.

pH and viscosity are the two dials. A volatile amine keeps the ink at pH 8.5–9.0 on press. As amine leaves, pH falls, the resin comes out of solution and viscosity rises. A pH stabiliser is supplied for long runs and hot pressrooms.

Drying is airflow, not temperature. High-velocity impingement at 70–90 °C with adequate exhaust removes water faster than higher temperature with poor airflow, and keeps heat-sensitive films flat.