Preventing migration of mineral oils and other contaminants from packaging containing recycled fibers to the packaged food product is possible, with the new coated papers for flexible packaging developed by Sappi in partnership with Basf and Eurofins.

The mineral oils used as solvents in inks can, during the process of recycling printed paper and board, remain in the cellulose fibers, which in such a way cannot be reused in order to produce food packaging due to the risk of contamination. Sappi has found a way to remove the obstacle and, in collaboration with Basf and the laboratory Eurofins, has developed two papers that act as barriers against those mixes of saturated (MOSH) and aromatic hydrocarbon (MOAH) based mineral oil mixes, which are suspected of being carcinogens.
The new materials, which are called MOB (mineral oil barrier) Kraft and MOB Gravure, took more than one year to develop, with various tests and pilot productions to guarantee optimal results. MOB Kraft, for the interior of bags, consists in MGBK (machine glazed bleach kraft) with a MOB on the back, and is available in formats between 80 and 120 g/mq. MOB Gravure is destined for rotogravure printed primary packaging, such as boxes, bags and wrapping, and is available in formats ranging from 95 to 140 g/mq; the top side is roto printed, and the MOB on the back protects the packaged product. Both paper types enable application of additional barriers, both dispersion and extruded.

Initial challenges
«One of the first challenges posed by the project was the creation of a homogeneous coating layer, covering 100% of the pre-coated paper support, since even the smallest defect compromises the quality of the barrier function. In order to guarantee it, we used a substrate that is extremely smooth, with low porousness, equipped with a good pre-coate, also with low porousness», explained Jos Lycops, Senior Product Specialist of Sappi’s central R&D. «And the other prerequisite for the success of our research was finding a way to obtain a “window” on the coating machine to apply the barrier layer without blocking on the reel».
Basf’s chemical knowhow proved decisive. «The task required developing an aqueous dispersion polymer system that could provide the required barrier; form a good, defect-free film at given parameters; and not block on the reels», stated Thomas Steinmacher, in charge of Application Technology at Basf. «Our longstanding relationship with Sappi and close collaboration on the project have enabled us to find the solution in a particularly timely fashion».

A custom test
In order to determine the effectiveness of the MOSH/MOAH barrier, the contribution of Eurofins Consumer Product Testing GmbH, specialized in testing and analysis of food products, pharmaceuticals, environmental samples and consumption products, proved decisive.
Commissioned by Basf, the German lab conducted a test cycle of 3 months. These and other tests proved that Basf and Sappi’s MOB coating papers prevent the migration of mineral oils for the standard period of preservation of food products. «In recent years we have made hundreds of analyses of mineral oils, applying the rigid standards of the federal German risk assessment institute», commented Andreas Grabitz, Technical Sales Manager of Packaging Materials at Eurofins. «This experience has enabled us to tailor tests for the specific requirements of this project, which saw a dramatic reversal: at first, safety regulators claimed that the migration of mineral oils could only be safely inhibited using functional barriers like internal bags. But in fact, the material tested by Basf is the first coating applied directly to the packaging material that complies with barrier property requirements».

The first user
«Thanks to this partnership – comments Rosemarie Asquino, Sappi Specialities Sales & Marketing Director – brand owners and converters can take advantage of the functional properties of our new products and, at the same time, maintain high environmental standards by using recycled packaging materials. And effectively, the market has responded without hesitation. We have already received our first order for the new MOB paper from a manufacturer of cartons for dry foods, as an alternative to material previously used, coated with PVDC, which is more costly and contains chlorine».
Sappi MOB Kraft and MOB Gravure are, moreover, highly versatile. They both find application in the packaging of sugar, chocolate and conserves, coffee and tea, bagged potato chips, snacks and peanuts, dry and dehydrated, frozen and deep-frozen foods.