Barrier-coated cellulose-based substrate, laminated packaging material and packaging container comprising the cellulose-based substrate
The present invention relates to a method for manufacturing a barrier-coated substrate web, coated with a layer of reduced graphene oxide. The invention further relates to laminated packaging materials comprising the barrier-coated substrate web, in particular intended for liquid carton food packaging, and to liquid carton packaging containers comprising the laminated packaging material.
1 . A 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
a) providing and forwarding the substrate material web,
b) providing an aqueous composition comprising from 0.1 to 15 weight-% of graphene oxide, from 0 to 5 weight-% of additives and from 85 to 99.9 weight-% of water, the 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 the substrate material web 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 on the substrate material web,
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 on the substrate material web,
g) forming a barrier-coated substrate material web with a dry layer of reduced graphene oxide by exposing the first dry layer of layered graphene oxide particles or flakes to the second dry layer of reducing agent for a minimum predetermined time at a minimum pre-determined temperature, and
performing a further step i) and/or a further step h) before step g),
wherein the step i) is coating or laminating the substrate material web with a further layer of a polymer to cover the second dry layer of the reducing agent, and
wherein the step h) is winding the coated and dried, substrate material web onto a reel.
2 . The method according to claim 1 , wherein the concentration of the graphene oxide in the aqueous composition is from 0.5 to 15 weight-%.
3 . The method according to claim 1 , wherein the wet coated thickness of the aqueous composition of graphene oxide is from 10 to 400 μm.
4 . The method according to claim 1 , wherein the reducing agent is selected from the group consisting of sodium citrate, ascorbic acid (vitamin C), lemon juice, vinegar and green tea.
5 . The method according to claim 1 , wherein the reducing agent is ascorbic acid.
6 . The method according to claim 1 , wherein the concentration of the reducing agent is from 0.5 to 15 weight-%.
7 . The method according to claim 1 , wherein the substrate material web from step f), before or during step g) is irradiated to accelerate the reduction reaction taking place between the applied first and second dry layers.
8 . The method according to claim 1 , wherein the substrate material web is continuously forwarded at a constant speed.
9 . The method according to claim 1 , wherein the multilayer graphene oxide platelets have 2-10 stacked monolayer flakes of graphene oxide.
10 . A method for producing an oxygen barrier material for a packaging material, by coating a substrate material web with a layer of reduced graphene oxide, the method comprising:
a) coating an aqueous composition onto a substrate material web to form a wet coating on the substrate material web, the aqueous composition that is coated onto the substrate material web including from 0.1 to 15 weight-% of graphene oxide, from 0 to 5 weight-% of additives and from 85 to 99.9 weight-% of water, the graphene oxide including monolayer flakes of graphene oxide and multilayer graphene oxide platelets, having up to 20 stacked monolayer flakes of graphene oxide,
b) drying the wet coating on the substrate material web by forced evaporation to obtain a first dry layer of layered graphene oxide particles or flakes on the substrate material web,
c) applying an aqueous solution of a reducing agent onto the first dry layer of graphene oxide on the substrate material web to form a wet aqueous coating of the reducing agent on the substrate material web,
d) directly following step c) drying the wet aqueous coating of the reducing agent, by forced evaporation to obtain a second dry layer of reducing agent on the substrate material web,
e) forming a barrier-coated substrate material web with a dry layer of reduced graphene oxide by exposing the first dry layer of layered graphene oxide particles or flakes to the second dry layer of reducing agent for a minimum predetermined time at a minimum pre-determined temperature, and
performing a further step f) and/or a further step g) before step e),
wherein the step f) is coating or laminating the substrate material web with a further layer of a polymer to cover the second dry layer of the reducing agent, and
wherein the step h) is winding the coated and dried, substrate material web onto a reel.