Os materiais usados para embalagens flexíveis should be safe from different points of view. Food is not allowed to be in contact with external contaminant like bacteria, viruses, other microorganisms, dirt, so the microstructure of the package materials must not allow this dangers to pass through and contaminate food.
O polipropileno tem uma estrutura cristalina reticulada que é usada para umboa barreira para gases e contaminantes. So the polymers of polypropylene are widely used in food packaging, conferring a good protection. But some migrants could pierce the macromolecular structure of polymers and could contaminate the food stuff. Such migrants could be mainly the components of printing inks and of polyurethane adhesives.
Adesivos de poliuretano are a mixture of two polymers that reacts as temperatures around 30 to 50 degrees celsius. These two components suffer a polymerization process, and it strengthens.
Assim, este adesivo é usado paraligação do polímero impresso ao polímero metalizado.It is known that for package food in wraps, and bags, are used laminates. Preferred materials for food packaging often consist of a first substrate, such as a film, which is generally thin and transparent (about 30 microns), and can be printable, and a second substrate which can be another type of material often is thinner film about 20 microns, a metal foil, a metallised film or a transparent film.
O uso de adesivos de poliuretano reativos, em alguns casos, pode levar à contaminação dos alimentos embalados com isocianatos não reagidos e aminas aromáticas cancerígenas, formadas pela reação dos componentes dos adesivos com a umidade do alimento. Portanto,pesos de revestimento do adesivo used in lamination will be not higher than 1.5-5g/m². food packaging materials may release migration compounds which result from the adhesives used in manufacturing such materails.
