Method for forming a PVOH based barrier layer on a substrate

A method for the production of a packaging material comprising a substrate and a gas barrier layer based on polyvinyl alcohol (PVOH), said method comprising the steps of:

• applying a coating composition of said PVOH dissolved in a first solvent onto said substrate to form a coating;
• subjecting the coating to a first drying step to form a dried PVOH-based coating on said substrate, wherein the dried PVOH-based coating comprises regions of crystallized PVOH structures separated by regions of amorphous PVOH;
• contacting the dried PVOH-based coating with a crosslinking solution comprising a crosslinking agent in a second solvent, to effect crosslinking of the PVOH-based coating;
• and
• subsequent to the contact with the crosslinking solution, subjecting the PVOH-based coating to
• a second drying step, forming the PVOH-based barrier layer on said substrate;
• with the proviso that if the crosslinking solution comprises PVOH, the amount of PVOH added by the crosslinking solution is less than 20% (by weight) of the amount of PVOH added by the coating composition.