Polyester Co-Extrusion on Steel; Adhesion and Sterilisation Behaviour, 2003 European PLACE Conference Proceedings

Polymer coil-coated packaging steels are attracting more and more attention. Advantages compared to sheet and coil lacquered systems include the absence of volatile organic compounds (VOC’s) on coating application, the consistent quality of the application process and the absence of food legislation issues of the product. In 2000, Corus Packaging Plus (CPP) started-up a production facility for manufacturing extrusion coated packaging steel (Protact). The products are mainly positioned in the food markets (ends, deep-drawn cans, 2-piece beverage cans) and the most frequently applied polymer coatings are PET and PP in a typical thickness of 20 microns. Achieving adhesion of such a polymer coating to steel (typically TFS or tinplate) can be considered to be amongst the most difficult tasks in the process. On previous occasions, it has been shown that adhesion can be established by using (chemically) modified PET and PP resins. However, on processing of the polymer strip in the can making and food industries, the product is frequently subjected to highly demanding treatments such as forming (deep-drawing or wall ironing), thermal printing and sterilisation. This paper describes some developments with regard to polymer-coated steel for the aforementioned demanding applications, especially sterilisation.