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Graphic element Research > Growth > Research projects > Materials & technologies projects > The art of making a film
Graphic element The art of making a film

Consumer demands require producers of plastic packaging to achieve barrier properties as effective as metal or glass. Current vapour deposition processes for coating plastic films are inefficient and limited to metal deposition, although they are simple and there have been design improvements that allow better-directed evaporation characteristics. The result of a CRAFT project is a more efficient aluminium-coating process. And, more importantly, the technology can be used to coat silica to produce the latest packaging materials - transparent barrier films.

Silicon oxide vacuum deposition source, installed on a conventional web coating machine

The hectic pace of modern life means that we have little enough time to eat meals, let alone to prepare them. Hence, there is a huge demand for convenience food. This has stimulated the creation of new food products and packages such as TV dinners and pre-prepared meals, that are ready-to-eat or destined for the microwave.

To keep up with such consumer demand, packaging engineers have designed lightweight, durable packaging, using a combination of metal and plastic. Examples of goods already employing such packaging materials include shelf-stable meals, snacks like potato crisps and peanuts, and the ultra-light coffee 'brick packs'.

Coating with metal

The standard method for manufacturing these materials is by evaporation or vapour deposition - aluminium is heated under vacuum until its vapour is given off, which then cools, depositing a solid, which forms the coating. The problem is that the coating process has low efficiency, and most of the aluminium ends up on the equipment and not on the plastic film.

Making these thin coatings can be considered as a high-tech spray painting process. The process could be controlled better if it was modified - similar to the fitting of a guide or nozzle to a paint sprayer. Aluminium could then be directed towards the plastic film and not the coating machinery.

This was the idea behind the CRAFT project 'Directed high rate evaporation of metallic and transparent materials on to polymer films'. A group of ten partners, including SMEs in the European packaging industry, collaborated on the project. Their main objective: to help improve the efficiency of the standard manufacturing process for making aluminium-coated films.

Project co-ordinator was Dr Horst-Christian Langowski, head of the Materials Development Department and deputy director of the Fraunhofer Institute for Process Engineering and Packaging (IVV) at Freising near Munich. "Our institute carried out some basic research in the mid 90s," Dr Langowski explains. "This patented work formed the basis of the project. We found project partners from the whole production chain: material suppliers, process equipment manufactures and plastic film converters. We also recruited the end users - the food fillers or packers - which were interested in the new types of packaging materials such as transparent barrier films."

Forming a European network

Transparent, flexible, silica-coated plastic films are produced in Japan, but they are expensive. In Europe, there are only a few small-scale production units. Therefore, as Dr Langowski stresses: "European collaboration made a lot of sense in the set-up of this CRAFT project for SMEs. It has already formed the basis of a network to transfer technology on new processes and packaging materials throughout Europe."

New heating equipment was developed by Wolfram Industrie (Germany). Some coating materials and engineering components were made by FN (previously Fabbricazioni Nucleari) in Italy. These companies helped initiate the project.

Two SMEs, Stampfoil (Italy) and Ultimet (United Kingdom), carried out vacuum coating experiments in production. Hueck Folien (Austria) and Bolloré (France) scaled up production from the laboratory level. Alfa Roto (Greece) and Ecoform Multifol (Germany), two laminating firms, processed the coated films into ready-to-use packaging films. The University of Ioannina (Greece) evaluated the flavour permeability of these final films.

The Fraunhofer Institute completed most of the laboratory work, designed components, supervised installations and experiments, and co-ordinated the whole project.

  Developing new films

The project has achieved its goals. The new technology can be simply fitted to the existing production equipment. The primary benefit of the technology is that it allows coatings to be made from materials other than aluminium, namely silicon oxide or chromium. From now on, in Europe, transparent barrier layers of silica can be deposited on to plastic films with only minor changes to the standard aluminium-coating equipment. Moreover, primer layers, such as chromium, can be deposited - an important feature for some technical applications.

Most of the material (about 80%) is deposited on the plastic film and not on the coating machines as previously experienced. This feature may also be a benefit for the standard aluminium material, but the more complex shape of the evaporation sources ('boats') makes the replacement of the conventional aluminium boats more difficult.

The project was completed in 1999, and the SME partners are grasping the opportunity to make silica-coated films. These transparent films will be used to pack perishable food products, and will have a significant effect on the annual turnover of the SME film makers involved in the project. The figures are difficult to quantify, but conservative estimates predict a minimum combined annual increase of euro 5 million.

Dr Langowski concludes: "The project's success does not stop there. We have several other spin-offs of the new technology in the pipeline. These mainly concern finding new opportunities for other products that could be made using versions of the same basic technology that we have developed. These could include technical films such as special intermediate adhesive layers inside heavy-duty capacitors for the electrical industry."

Coating with metal
Forming a European network
Developing new films

Key data

Development of improved materials is part of the New materials and production technologies generic action. This CRAFT project provides SMEs with an improved manufacturing technology for the metalic coating of plastic film used in packaging.

Project: Directed high rate evaporation of metallic and transparent materials on to polymer films (BRST-CT97-5116)

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