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
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.
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
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.
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.
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.
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
a European network
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."
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.
SMEs, Stampfoil (Italy) and Ultimet
(United Kingdom), carried out vacuum coating experiments in production.
(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
Fraunhofer Institute completed most of the laboratory work, designed
components, supervised installations and experiments, and co-ordinated
the whole project.
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.
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.
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
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