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Pushing the Barriers: Coatings suppliers tackle mineral oil migration

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Pushing the Barriers: Coatings suppliers tackle mineral oil migration

September 16, 2014 - 08:04

New barrier coatings and grades for paper-based packaging are part of the push forward to protect against mineral oil migrations into food. The risks of possible health damaging mineral oil residues migrating from recycled board and paper to food hit global headlines two years ago causing a high profile media storm.

As cardboard packaging is often produced from recycled waste paper, such as newspapers, these can have residues of printing ink that are not approved for food contact, and cannot be completely removed in the recycling process. Scientific tests at the time showed that mineral oil hydrocarbons were found in Advent calendar chocolates.

In the controversy that ensued, the German government recommended functional barriers for mineral oils to prevent contact between mineral oil residues and the food, and legislation is currently underway to formalize the situation.

With impending legislative change on the horizon coating suppliers are upping their game and paper and board producers are developing new grades with increased barrier qualities.

BASF has made considerable headway in developing solutions to combat the risks of migration. BASF has developed various barrier solutions that are applied to the internal surface of the cardboard box. According to the company, these extremely thin coatings are made from polymers or sometimes termed ‘macromolecules' - made up of many repeating smaller molecules. Barrier coatings that are only 10-15 micrometers thick - by comparison a hair is 120 micrometers thick - already protect food from the contaminants for up to three years. Products like noodles that remain for an average of 15 to 24 months in the packages, are reliably protected.

Heiko Diehl, the BASF manager responsible for the paper chemicals division, explains: "The most important requirement for the barriers is that the breakthrough time - which is the period until a barrier can become permeable and allow health hazardous substances to penetrate into the food is longer that the shelf-life of the packaged product.

"Our barrier coatings can be imagined as being like a close meshwork that allows only certain molecules to pass through," continues Diehl.

According to BASF, only very small molecules like water vapor can pass. Larger molecules like mineral oil residues cannot cross. In addition, the polar nature of the BASF barriers hinders the migration of the molecules.

BASF said that developing the barrier effect for large molecules was not the only challenge when designing the various coating solutions. The coating has to be flexible enough to stop fractures when the cardboard is folded and has to be capable of being easily removed in the recycling process.

The company works closely with one of Europe's leading manufacturers of folding cartons and boxes, Van Genechten in Kempten in Germany. The company processes about 200,000 tonnes/yr of cardboard. Michael Avemarg, innovation manager for materials says: "We anticipate that strict limits will be imposed and have already modified our production lines. To develop optimal coating solutions for our manufacturing process, we are already cooperating with BASF and testing products in our plants." For the jointly developed WLC Food Safe coating based on BASF's plastic Ultramid, the company won the German Packaging Prize last year.

Sappi Fine Paper Europe is also addressing concerns about migration.

Developed in partnership with BASF and Eurofins the company has launched Algro Guard M and Leine Guard M barrier paper grades. The grades were developed to allow brand owners to use their current recycled fiber based folding boxes, shelf ready packages and transport boxes. The food inside is protected by inner bags, pouches and sachets manufactured from the Sappi mineral oil barrier papers.

"The integrated solution of mineral oil barrier functionality combined with excellent heat sealing properties minimize converting process steps and considerably reduce costs in the supply chain," comments René Köhler, product group manager Flexpack Sappi Fine Paper Europe.

Mayr-Melnhof Karton's product contribution to the mineral oil migration issue is the result of a two-year comprehensive test project with leading multinational food producers. The end result is its cartonboard product FoodboardTM, which has a distinctive functional barrier on the food contact side of the board.

Careful consideration has also been given to how the board performs once it is on the converting line. The company states that two million boxes produced so far is evidence of high converting standards and fast packing line performance. FoodboardTM is also in full compliance with the provisions of the currently discussed and pending mineral oil regulation.

Significant investment has gone into the production of FoodboardTM and the Austrian parent mill of Mayr-Melnhof Karton in Frohnleiten will be supplying the product by the end of this year.

Direct migration isn't the only concern regarding mineral oil. Not wanting to leave any stone unturned Metsä Board has looked into the subject of ‘indirect migration' - conducting a study based on the presumption that mineral oils migrate from recycled fiber based transport packaging, through the food package and into the food itself.

The company's folding boxboards are manufactured from fresh forest fibers, which have been approved for direct food contact. The indirect migration study was carried out where mineral oil content, both in dry food and in packaging materials, was measured after one, two, five, seven and 11 months storage time.

Fresh forest fiber based folding boxboard cartons were packed in high density polyethylene recycled fibers. All dry food samples were received direct from the customer's mill, and stored in their original packaging. They were then compared to an unpacked sample of the same food, which had been wrapped in aluminum to protect it from any external contamination.

According to Pirita Suortamo, senior R&D engineer at Metsä Board R&D Centre there was no increase in harmful mineral oil content either in the food or in the cartons. This was also proven by analyzing the same type of product purchased from a local supermarket - that had gone through the whole transportation chain.

Suortamo is, however still concerned over direct migration. "To avoid this risk only fresh fiber based board is recommended. It is also important to pay attention to other packaging components and to make use of the best possible design to avoid migration," she adds.

Prevention is better than cure

The prevention is better than cure theory is working well for Sun Chemical. Its launch of its fourth edition low migration guide entitled: ‘Designing Packaging with Certainty - A Best Practice Guide has proved to be an extremely useful tool for converters - with around 5,000 copies being shipped to date.

The guide is laid out in a logical sequence to help readers understand how to design, produce and store packaging safely with respect to migration of unwanted contaminants, and provide practical ways to minimize the risks. The company aims to address the most important questions from the viewpoint of inks and coating manufacturers.

Support is key according to Jonathan Sexton, European product manager energy curing. He says: "Our guide can be a great support to the packaging development workflow in the production of safe packaging for food and sensitive applications such as tobacco and pharmaceuticals. We are a very supportive partner for brand owners on this issue."

Printing ink manufacturer Domino is tackling the subject from a much earlier stage by ensuring that ink used on the packaging contains no mineral oils in the first place. It has developed MOF 950BK, which contains no harmful substances, is fully sustainable and based on organic raw materials.

Andrew Gunton, product manager - fluids at Domino comments: "We have taken a proactive stance by developing an environmentally friendly mineral oil-free ink for our C6000 outer case coding solution. This gives brand owners and manufacturers complete peace of mind that their food products will remain free from mineral oil contamination."

Giving customers peace of mind before any legislation comes into play is key. Smurfit Kappa's new solution Catcher Board MB12 uses a method that creates a blocking mechanism across the surface area of the packaging including at the ‘cut edges' of the board. Made using natural ingredients, the new board will be introduced as white lined chipboard and solid board.

A Smurfit Kappa spokesperson says: "In addition to blocking mineral oil migration across the whole surface area of the packaging, the product feels and reacts just like normal board during the manufacturing process. This means our customers won't have to change any of their packaging processes.

"If European legislation is introduced we believe we will be in a position to offer an innovative product to our customers that will meet new regulatory requirements."