Sealing materials in contact with food

Over the years, the EU Plastics Directive has developed to become the most comprehensive set of rules for packaging in contact with food. Numerous amending directives, positive lists for additives and monomers, specified limit values for individual substances and details on the scope of declarations of conformity through to the so-called "Super Regulation" and the Plastics Implementation Measure (PIM), have extensively documented the requirements to be complied with. For sealing materials, these include the fact that under normal, predictable conditions of use, no components of the sealing material may migrate into food in volumes which could represent a risk to human health. Nor may there be any unacceptable change in food composition and the organoleptic properties of food – smell, taste, appearance – must not be impaired.

Accordingly, each individual component of the sealing material must be examined critically in terms of a possible hazard potential. These raw materials must be firmly integrated in the sealing matrix so that they cannot be rinsed out. Nor may auxiliary agents used during processing (e.g. organic solvents, interlinking chemicals) leave any residue in the sealing material.

These requirements speak for TPE materials available in granulate form which are shaped as required by means of thermal forming processes. Interlinked or other reactive additives are not necessary with the result that nothing can migrate.

One reason for developing PROVALIN®, the first and to date only sealing compound free of PVC and plasticizers for metal vacuum closures. A wide range of applications is meanwhile available enabling practically all requirements involving contents, closing processes, storage and closure sizes to be complied with. All types of contents can be safely packaged beyond the overall BBD. There are no restrictions during the filling and sealing process, including hot or cold filling or even thermal post-treatment such as pasteurization and sterilization. After a lengthy and complex development phase and an initially gradual introduction phase, this PVC-free closure has meanwhile become a success story: the 100 millionth PVC-free closure was celebrated in spring 2013.

Manifold requirements on closure solutions

The requirements on closure solutions protecting products in the food and beverages industry in particular are not only extremely varied – they are often very specific, whereby selection of the suitable compounds is influenced by

beverage containers – glass bottles or PET, disposable or reusable packaging

stress – changing temperatures, transport and storage, rate of circulation, head pressure, clear traces of usage, material abrasion

closures – crown corks, plastic or vacuum closures

filling – cold, cold-aseptic, hot, pasteurization, sterilization

beverages – fruit juices, fizzy soft drinks, fizzy or still alcoholic beverages, mineral water, milk and dairy products, tea, sensitive contents etc.

which are developed and optimized in close cooperation with the manufacturers of closures and brand items.

In the case of beverages in particular, one key factor is represented by retention of the original organoleptic properties, neutrality in terms of taste (especially for mineral water), aroma and protection from foreign odors incurred during transport and storage.

Where highly-carbonated alcoholic beverages are involved, sealings of the maximum technical level are required. As is a barrier function. Barrier compounds display an increased barrier effect when it comes to penetration by a wide variety of gaseous substances, including oxygen, 2,4,6 Trichloranisol (TCA)* and other volatile organic compounds which can lead to sensory deterioration in the case of beer, juices and other contents. Carbon dioxide emissions from the bottle are significantly reduced. In this environment – as in bottle ageing for champagne and sparkling wine – Peak-Free® technology is particularly popular for applications involving sensitive contents. Scavenger compounds also have an oxygenating effect as they absorb the oxygen present in the sealed bottle and prevent penetration by oxygen from the outside. In the form of scavenger compounds on the one hand and barrier compounds on the other, two different technologies are available for protecting sensitive contents from influences affecting taste as well as extending the shelf life.

As already described for the materials used in medical technical applications, it can also be of importance in the food sector that the compounds can be sterilized, e.g. for contents such as dairy products.

Creative freedom – especially for promotion campaigns, marketing purposes, product launches, marking for traceability or brand protection – is provided by laser-arkable seals. This is where the most demanding requirements are often made on marking closure seals. Solutions are offered by the in-shell and out-shell process, whereby not only alphanumerical codings are possible but even complex graphics and logos can be reproduced in detail. PVC-free Polyliner® products offered by Actega DS – with FDA and EU approval – are free of heavy metals while optimum results are achieved using an Nd:YAG laser.


PVC-free production methods and high-performance TPE are the things of the future. And not only because of the practically impossible challenges outlined by the FDA and EU (e.g. Plastics Directive, Ordinance on Medical Devices). It has long been obvious that there are numerous technical processing advantages, in some cases even involving significantly less expensive aspects and considerably more positive effects in terms of sustainability when TPE materials are used. And consumer and patient protection is also satisfied. A material with a long history and a great future.

* 2,4,6 Trichloranisol (TCA) is a chlorinated, aromatic hydrocarbon with an intensive moldy-musty odor. This phenol derivative is the main reason for a corky taste – the most significant olfactory-gustatory wine flaw.