embodiments herein relates to a bisphenol a - free multi - layer , such as a biaxially oriented polyester film , for lamination on metal sheets , which could be used for food containers . the bopet film has an outer release layer , which aids in the release of food , such as a high protein food source , when food is cooked and sterilized in direct contact with the outer release layer . the bopet film can be laminated to metals used in the manufacture of food containers with the outer release layer being exposed to allow a direct food contact between the surface of the outer release layer and food . more particularly , the invention relates to a novel outer release layer resin composition comprising an ultra high molecular weight siloxane polymer and a polyethylene trephthalate resin . optionally , an alkali - metal phosphate and a phosphoric acid compound can be added , during polymerization the outer release layer resin composition , as a catalyst / additive package to the ingredients forming the outer release layer resin composition .