General Launches Vacuum Coating for Clear Barrier Packaging Films

With many types of packaged foods, consumers have always preferred to see the contents of what they are actually buying. This remains a developing trend but it has to be balanced against the requirements of the packaging itself. This must protect the product being sold, be environmentally friendly and safe, cost-effective and yet attractive enough to promote the sale of the packaged items.

Certain food packaging materials need to have light and ultra-violet (UV) barrier packaging to enable the food to stay fresh. This light sensitive food can be packaged using aluminium metallized film which also provides the necessary oxygen and moisture barriers. Other foods do not need this light barrier and can be packaged in transparent or clear barrier films.

Clear barrier films can be produced and are already available using atmospheric coatings, which are coatings applied to the film in atmosphere rather than in vacuum. However, General Vacuum Equipment (GVE) has recently developed and launched a vacuum coated clear barrier coating which combines the benefits of the atmospheric clear barrier coating with the additional advantages of a vacuum coated barrier layer.

Vacuum coating has the unique property of requiring only a small fraction of the thickness of the equivalent atmospheric coated layer to produce similar functionality. Typically, atmospheric coatings are measured in micrometres (10ˉ6m) and vacuum coated layers are measured in nanometres (10ˉ9m), with the barrier properties of the two structures being similar. This is potentially a huge environmental and economic advantage for vacuum coating technology.

General uses a standard aluminium metallizing machine as a foundation for this process and it is believed that two leading European converters have used their own similar systems for the past few years, successfully selling into markets worldwide.

GVE's technology uses the controlled injection of oxygen into the aluminium vapour stream causing a reaction between the two elements to produce aluminium oxide (AlOx). This compound can be transparent if the process conditions are correct.

The exciting feature of the GVE process is that a good water and oxygen barrier is achieved without the need for exotic and expensive vacuum ancillaries, such as plasma guns. The performance of the machine is based on a control loop which constantly monitors the optical properties of the coated substrate and also ties the injection of the oxygen in to the system and in to these properties.

By carefully examining and controlling these properties, both the oxygen and water vapour barrier properties across the width and length of the substrate can be guaranteed. This tight control also permits very low usage of process consumables, enabling low cost production of a relatively high priced coating.

The AlOx coating system is only available in new General K4000 metallizers. The system will work together with the standard aluminium metallizer coating system but provides the converter with two technologies in one machine.

GVE has been running AlOx trials on such a machine for the last 12 months and it is now available for coating customers' film whether PET, BOPP, CPP, PLA or other types of plastic film. Extensive barrier testing is also available on customers' coated materials.