权利要求：
CLAIMS
1 . A method for manufacturing a barrier layer for a paper or paperboard based packaging laminate, said method comprising: a) providing a barrier substrate comprising at least 50 wt% highly refined cellulose pulp (HRC) based on dry weight of the barrier substrate, said HRC having a Schopper-Riegler (SR) number above 80 as determined by standard ISO 5267-1 , b) providing a transfer coating substrate comprising a vacuum coating layer and a backing layer separated by a release layer, and c) transferring the vacuum coating layer from the backing layer to the barrier substrate by a transfer coating process using an adhesive layer applied on the barrier substrate and/or the vacuum coating layer to obtain a barrier layer for a paper or paperboard based packaging laminate.
2. The method according to claim 1 , wherein the barrier substrate is a freestanding barrier substrate film.
3. The method according to claim 1 , wherein the barrier substrate is a coating layer on a paper or paperboard substrate.
4. The method according to any one of the preceding claims, wherein the barrier substrate has a grammage in the range of 2-100 g/m2, preferably in the range of 2- 60 g/m2, and more preferably in the range of 20-50 g/m2.
5. The method according to any one of the preceding claims, wherein the barrier substrate comprises at least 70 wt%, preferably at least 90 wt%, highly refined cellulose pulp based on the dry weight of the barrier substrate.
6. The method according to any one of the preceding claims, wherein the highly refined cellulose pulp has a Schopper-Riegler (SR) number above 85, preferably above 90, as determined by standard ISO 5267-1 .
7. The method according to any one of the preceding claims, wherein the highly refined cellulose pulp is a microfibrillated cellulose (MFC).
8. The method according to any one of the preceding claims, wherein the barrier substrate has a Gurley Hill value above 5000 s/100ml, preferably above 20 000 s/100ml, and more preferably above 42 300 s/100ml, as measured according to standard ISO 5636-5.
9. The method according to any one of the preceding claims, wherein the barrier substrate has a moisture content of 1 .5 wt% or more, preferably 2 wt% or more, more preferably 3 wt% or more or 3.5 wt% or more or 4 wt% or more, as determined according to ISO 638.
10. The method according to any one of the preceding claims, wherein the barrier substrate has a water vapor transmission rate (WVTR), measured according to the standard ASTM F1249 at 50% relative humidity and 23 °C, of above 30 g/m2/24h.
1 1 . The method according to any one of the preceding claims, wherein the transfer coating process comprises contacting and adhering the vacuum coating layer to the barrier substrate using the adhesive layer applied on the barrier substrate and/or the vacuum coating layer, and removing the backing layer, leaving the vacuum coating layer, and optionally the release layer, on the barrier substrate.
12. The method according to any one of the preceding claims, wherein the vacuum coating layer in contact with the barrier substrate via the adhesive layer is subjected to pressure, heat, and/or radiation to improve adhesion between the vacuum coating layer and the barrier substrate.
13. The method according to any one of the preceding claims, wherein the backing layer comprises a plastic film.
14. The method according to any one of the preceding claims, wherein the release layer comprises a layer of a material having lower adhesion to the backing layer or to the vacuum coating layer than the adhesion of the adhesive layer to the barrier substrate and to the vacuum coating layer.
15. The method according to any one of the preceding claims, wherein the release layer comprises a layer of a material having lower adhesion to the backing layer than to the vacuum coating layer, or having lower adhesion to the vacuum coating layer than to the backing layer, such that the entire release layer remains on the vacuum coating layer or on the backing layer when the backing layer is removed.
16. The method according to any one of the preceding claims, wherein the vacuum coating layer comprises an inorganic vacuum coating layer, such as a metal, metal oxide, or ceramic vacuum coating layer, preferably an aluminum or aluminum oxide vacuum coating layer.
17. The method according to any one of the preceding claims, wherein the vacuum coating layer comprises an organic vacuum coating layer.
18. The method according to any one of the preceding claims, wherein the vacuum coating layer has a thickness in the range of 10-600 nm, preferably in the range of 10-250 nm, and more preferably in the range of 50-250 nm.
19. The method according to any one of the preceding claims, wherein the adhesive layer comprises at least 50 wt% of an adhesive polymer or mixture of adhesive polymers based on dry weight.
20. The method according to any one of the preceding claims, wherein the adhesive layer comprises one or more adhesive polymers selected from the group consisting of polyolefins, polyurethanes, and acrylic copolymers.
21 . The method according to any one of the preceding claims, wherein the adhesive layer comprises at least 50 wt% of a water-soluble polymer or mixture of water-soluble polymers based on dry weight.
22. The method according claim 21 , wherein the water-soluble polymer is selected from the group consisting of a polyvinyl alcohol (PVOH), a carboxymethyl cellulose (CMC), a starch, an alginate, and a hemicellulose, preferably a PVOH.
23. The method according to claim 21 or 22, wherein the adhesive layer further comprises a crosslinking agent capable of crosslinking the water-soluble polymer, preferably an organic acid, and more preferably citric acid.
24. The method according to any one of claims 21 -23 wherein the adhesive layer further comprises up to 50 wt% of microfibrillated cellulose (MFC), nanocrystalline cellulose, a chemically modified cellulose derivative such as sodium carboxymethyl cellulose, hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, cellulose acetate, hydroxyethyl cellulose, a hemicellulose, or a combination thereof, based on dry weight.
25. The method according to any one of the preceding claims, wherein the obtained barrier layer has an oxygen transmission rate (OTR), measured according to the standard ASTM D-3985 at 50% relative humidity and 23 °C, of less than 10 cc/m2/24h, preferably less than 5 cc/m2/24h, and more preferably less than 1 cc/m2/24h.
26. The method according to any one of the preceding claims, wherein the obtained barrier layer has a water vapor transmission rate (WVTR), measured according to the standard ASTM F1249 at 50% relative humidity and 23 °C, of less than 10 g/m2/24h, preferably less than 5 g/m2/24h, and more preferably less than 1 g/m2/24h.
27. A method for manufacturing a paper or paperboard based packaging laminate, said method comprising: i) providing a paper or paperboard substrate, and
ii) providing a barrier layer manufactured according to the method defined in any one of claims 1 -26 on the paper or paperboard substrate to obtain the paper or paperboard based packaging laminate.
28. The method according to claim 27, wherein step ii) comprises laminating a free-standing barrier layer manufactured according to the method defined in any one of claims 1 -26 to the paper or paperboard substrate.
29. The method according to claim 27, wherein step ii) comprises laminating a barrier substrate comprising at least 50 wt% highly refined cellulose pulp (HRC) based on dry weight of the barrier substrate to the paper or paperboard substrate and then transferring the vacuum coating layer from the backing layer to the barrier substrate as defined in any one of claims 1 -26.
30. The method according to claim 27, wherein step ii) comprises coating the paper or paperboard substrate with a coating dispersion comprising at least 50 wt% highly refined cellulose pulp (HRC) based on dry weight of the coating dispersion and drying the coating dispersion to form a barrier substrate on the paper or paperboard substrate, and then transferring the vacuum coating layer from the backing layer to the barrier substrate as defined in any one of claims 1 - 26.
31 . A barrier layer obtained by a method according to any one of claims 1 -26.
32. A paper or paperboard based packaging laminate obtained by a method according to any one of claims 27-30.