Flexo printing inks

Flexo Printing inks are based on very different ink systems. They are either solvent- or water-based or, in the case of UV inks, have a radiation-curing system. What they have in common is that they are made up of color pigments, binders, solvents, auxiliaries and additives. In the case of UV inks, photo-initiators are also added. Why are such different ink systems needed in flexographic printing? Lets looks at different types of flexo printing inks in detail.

For each ink system, there are clear areas of application for which the inks are particularly suitable. The decisive factor is the particular binder used in the ink system.

Flexible packaging: Solvent-based inks are most commonly used in this application segment, where they have a share of about 80%. A very common as well as versatile ink type is printing inks where nitrocellulose (NC) is the basis for the binder. Recently, polyurethane-based inks (PUR) have been used more and more. Both ink systems complement each other very well in their properties. While NC-based inks are used in surface and lamination printing, PUR inks have their weakness there. On the other hand, PUR-based inks show their strengths in applications such as pasteurization and sterilization of foodstuffs, for which NC-based inks are not suitable.

In Europe, there has been increasing demand for water-based ink systems for several years. Their share is around 15%, with a focus on the non-food sector. There, they are often used for printing plastic carrier bags. Today, their use in the food sector is increasing, as they are generally well suited to applications in flexible packaging and have the advantage of requiring virtually no volatile solvents (VOCs). 

UV inks are only used to a limited extent in flexible packaging due to their migration potential in the food sector. With a share of approx. 5%, they are limited to applications in narrow web printing.

Label printing: In label printing, on the other hand, UV inks are the most widely used ink technology. There, they have a share of approx. 80%. What is their advantage in label printing? They have good adhesion to a wide variety of materials, dry quickly and have a high gloss. 

Solvent-based inks are also used in label printing, where they have a share of 15% and are mainly used for printing on plastic films. Water-based ink systems have the smallest share in label printing. They are used both on film materials and on absorbent substrates.

Corrugated board printing: Water-based ink systems dominate in corrugated board printing. Their share is 100%. The decisive factor for this non-competitive position is the good drying behavior of water-based inks on absorbent substrates.

And then there is the question of what functions auxiliaries and additives have in an ink formulation? They are used to make very individual adjustments. For example, to adjust the properties of the ink film in terms of rub resistance, flexibility and slip behavior, or to adjust the printing inks in terms of their foaming or optical density.

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