Film & Foil


FLEXIBLE FOILS AND METALLISED MATERIAL POSSIBILITIES


By Tom Kerchiss, RK Print Coat Instruments


of reasons. From a raw material perspective, aluminium in its raw state: bauxite, is exceptional in that it is one of the most common materials on the planet. It is however subject to some controversy and scrutiny by environmental stewards. Some say that because the manufacture


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of even a single tonne of aluminium may involve upwards of 1 500 W/h electrical energy to convert bauxite into aluminium through the process of melt-electrolysis that this is not only wasteful but environmentally damaging. Foil advocates counter by saying that this in more than offset by the fact that when processed the material itself is both lightweight and thin. Some might say that this is a ‘case of a little going a very long way,’ something that every packaging converter can attest too. Any waste produced is combustible and as part of a household waste stream allows for the possibility to recover thermal energy from an incineration process rather than simply for any scrap to be directed to landfill. When it comes to packaging, alu-foil is


often used as part of a laminate and may be produced in widths of 2 metres and is then rolled out to thicknesses of as little as 6 microns. Foil used in beverage packaging


42 September 2020


luminium foil is one of those materials that garner a lot of attention, sometimes not for the best


most commonly has a thickness of 6.65 microns, which produced in widths of 2 metres x 100 equates to 55m2 of packaging, or taking into account other components of the laminate - approximately 666 litre packs of fruit juice. The barrier properties of foil are superior


to many of the other materials associated with packaging production. Even the sheerest of foil when used in combination with filmic structures such as those associated with pouch production makes for a product that is impervious to liquids, gases and light. Foil is not of course the only processing


option. In situations where the marketer and brand owner seek to attract consumers with a reflective or shimmering look, and when barrier resistance is not quite so important, then metallised film may be considered appropriate. The process of metallisation can be undertaken by air-to- air systems or via roll-to-roll systems. The process involves coating a plastic film with an extremely thin metal layer of around 10 to 18 microns under vacuum conditions onto a continuously moving web. The success of the process is dependent


upon a number of factors such as good adhesion to the substrate, uniformity of appearance and precise tension control of the web. Normally metallisation is not the


final process, subsequent converting processes to produce a saleable product may include cross cutting, varnishing, lamination and printing. The radiance of foil, metallised films,


papers and speciality inks (ink – incorporating alu-platelets, etc) have long been appreciated for their ability to convey prestige and quality to many a packaging product. Converters sometimes print reels of pre- metallised materials such as polypropylene (PP) in single ply on flexo or gravure presses. An alternative option is to laminate metallised oriented polypropylene (OPP) to another film prior to printing. If other films are involved processing options may vary. For instance, with a substrate such as a polyester the tendency is to laminate to the backing film prior to printing. Sometimes metallised polyester is reverse printed prior to laminating. No process is completely trouble-free,


every process, material and consumables used are subject in one way or another and at different times to processing variables. Even foil when used as a layer within a lamination can be problematic, especially as foil tends to be ultra- thin. The foil is often prone to microscopic nicks as it travels at high speed through the laminator; metallised films can also be


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