Barrier-coated cellulose-based substrate, laminated packaging material and packaging container comprising the cellulose-based substrate

Method for producing an oxygen barrier material for a packaging material, by coating a substrate material web with a layer of reduced graphene oxide, comprising the steps of

• a) providing and forwarding a substrate material web,
• b) providing an aqueous composition comprising graphene oxide including monolayer flakes of graphene oxide and multilayer graphene oxide platelets, having up to 20 stacked monolayer flakes of graphene oxide,
• c) coating the aqueous composition of graphene oxide onto the surface of the substrate material web while it is being forwarded,
• d) drying the wet coating of aqueous graphene oxide on the substrate material web, by forced evaporation, to obtain a first dry layer of layered graphene oxide particles or flakes,
• e) applying an aqueous solution of a reducing agent onto the first dry layer of graphene oxide on the substrate material web,
• f) directly following step e) drying the wet aqueous coating of the reducing agent, by forced evaporation, to obtain a second dry layer of reducing agent, and
• g) allowing the reducing agent of the second dry layer to reduce the graphene oxide of the underlying, first dry layer, during a minimum predetermined time at a minimum pre-determined temperature, to form a barrier-coated substrate material web with the dry layer of reduced graphene oxide.