Increasingly, UV curable inks and varnishes are used for food packaging applications. Conventional UV ink chemistry can lead to an unacceptably high level of contamination caused by incomplete cross-linking due to the presence of oxygen. Uncured monomers and photoinitiators can also migrate through the base material causing contamination of the contents.
Reducing the level of oxygen significantly improves surface cross-linking with a commensurate reduction in odour. Specially formulated inks can also reduce the causes of initiator migration. GEW have developed a simple method of oxygen removal with a new design of system.
GEW’s e-System inert
GEW have developed a compact system in which a sealed curing chamber is built around a small idler roller. Oxygen is purged from the chamber using nitrogen gas, which is introduced in a controlled manner via a “nitrogen knife” at the web inlet and via an injector in the curing chamber. An oxygen sensor within the chamber continuously monitors the oxygen level, which is displayed on the control unit in parts per million.
Controlling the oxygen level within the curing chamber is simply a matter of adjusting the nitrogen flow rate until the desired reading is achieved. For critical applications an alarm can be set to activate should the oxygen level exceed a user-defined limit. As an additional feature, the idle roller can be water-cooled to provide superior web temperature control. This reliable system is both frugal on nitrogen consumption and simple to use.
Applications
- Low odour inks for food packaging
- Degussa Goldschmidt siliconising – manufacture of release liners
- High speed printing up to 400 m/min
- Reduced initiator inks for lower printing costs
- Compact design lends itself to installation on most web presses
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