Method for producing a polymer coated metal strip and polymer coated metal strip produced thereby

A method for producing a polymer coated metal strip in a continuous coating line, the method comprising the subsequent steps of:

• providing a metal strip;
• providing one or more thermoplastic polymer films for coating onto at least one side of the metal strip;
• laminating the one or more thermoplastic polymer films onto the metal strip to produce a polymer coated metal strip;
• post-heating the polymer coated metal strip to a temperature sufficiently high to melt the one or more thermoplastic polymer films in order to reduce the orientation and crystallinity of the one or more thermoplastic polymer films to the target value;
• cooling the post-heated polymer coated metal strip;
• in-line illuminating the one or more laminated polymer films with near-infrared light having one, more or all wavenumbers between 3500 and 9000 cm−1;
• in-line acquiring back-scattered near-infrared light with a near-infrared spectroscopy detector;
• calculating a near-infrared spectrum from the back-scattered near-infrared light;
• determining the degree of crystallinity and/or the molecular orientation of the one or more thermoplastic polymer films by comparing the calculated near-infrared spectrum to a near-infrared spectrum of a reference material to determine a Conformity Index as a measure of the degree of crystallinity and/or the molecular orientation of the one or more thermoplastic polymer films.