Improving the safety of multi-layer packaging with regard to chemical migration

5 Improving the safety of multi-layer packaging with regard to chemical migration 

For those products laminated using reactive polyurethane based adhesives, suppliers have been aware for many years of the potential migration of amines formed by the reaction of unreacted isocyanate monomer with water and recommend that laminated products are given time to fully cure before they are used in contact with food. Adhesives have been developed that contain low levels of monomeric aromatic isocyanates, in order to reduce any potential migration of aromatic amines into food in critical applications. Such adhesives are not considered to present any notable amine migration hazard unless used in high-temperature applications. 

FDA regulations only allow the use of aliphatic isocyanates in laminating adhesives for high-temperature applications. (Cured aromatic systems can decompose to regenerate isocyanate and thus form aromatic amines at retortable or boiling water temperatures.) Discussions with a number of UK packaging producers revealed that they are aware of the need to use adhesive systems 

Sample 8 2 hours at 70 °C 19.5 Not examined under this test condition  

Laminating adhesive is always behind a barrier film layer. The thickness of this layer, the levels of crystallinity as well as polymer type all influence the migration rates of adhesive components through this layer. The rate of permeation of food or food simulant into the packaging is also controlled by the nature of the food contact layer. Because of the presence of this barrier layer between the adhesive and the food, it is only low molecular weight mobile chemical species that have the potential to contaminate food. 

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