Go solventless, says ETI

ETI Converting Equipment has specialized in developing coating stations on its Cohesio machine to manufacture complex laminate structures from a wide range of substrates. This process involves different types of solvent-less coating technologies. ETI’s silicone application station relies on the use of free radical silicone curing. Free radical silicone offers the advantages of the use of a very compact coating unit. There is no post curing; the silicone that is coating is immediately ready for the subsequent coating of the adhesive and final lamination, which allows a lot of flexibility in the choice of substrates and a wide range of release values.

Solvent-based silicones require larger units to provide the heat needed to cure the silicone, raising the capital investment needed. The high temperature of the process also limits the type of material that can be used. Finally, there is post-curing involved.

Free radical silicone requires a state of the art coating unit in order to be properly cured. This curing relies mostly on the need for an inert atmosphere (oxygen free) and properly designed UV lamps. The oxygen level needs to be maintained at very low levels - under 50 ppm - in order to avoid the reaction of non-polymerized silicone mixing with the oxygen and preventing the silicone from curing. The latest ETI unit has been improved by optimizing the seal around the entrance of the chamber, allowing a reduced consumption of nitrogen.

The free radical silicone needs a UV light with a strong element of UV-C rays. To keep the air in the nitrogen chamber tight, a quartz glass has been installed between the chamber and the UV system.

The silicone can be applied in a pattern if needed, reducing overall consumption. With the Cohesio, the liner can be printed before applying the coating. This unit allows for the production of linerless labels as well. In this application, the facestock is printed