BARRIER-COATED CELLULOSE-BASED SUBSTRATE FOR LAMINATED PACKAGING MATERIAL

Abstract

The present invention relates to a barrier-coated cellulose-based substrate and to a method of manufacturing such cellulose-based substrates, by dispersion coating of a ductile base layer pre-coating and subsequent dispersion coating of a gas barrier composition and/or vapour deposition coating of a barrier deposition coating.

Claims

1. Barrier-coated cellulose-based substrate, for use as a gas barrier sheet in a laminated packaging material for oxygen-sensitive products, comprising a cellulose-based substrate having a density of at least 900 kg/m.sup.3, and a grammage from 30 to 80 g/m.sup.2, and applied on a first side of the cellulose-based substrate, at least one gas barrier coating of at least one gas barrier material to a total thickness from 2 to 7000 nm, the gas barrier material excluding nanocrystalline cellulose, NCC, wherein the barrier-coated cellulose-based substrate further comprises a ductile base layer pre-coating, which is applied by dispersion coating and subsequent drying, onto the surface of the first side of the cellulose-based substrate and positioned beneath the at least one gas barrier coating, the barrier-coated cellulose-based substrate thus being suitable for providing gas barrier properties in a laminated packaging material and in packages made thereof.

2. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the gas barrier coating is a barrier dispersion coating, applied by dispersion or solution coating, and/or a barrier deposition coating, applied by a vapour deposition method.

3. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the barrier dispersion coating comprises a polymer selected from the group consisting of vinyl alcohol polymers and copolymers, such as from the group consisting of polyvinyl alcohol, PVOH, and ethylene vinyl alcohol, EVOH, starch and starch derivatives, xylan, xylan derivative, nanofibrillar/microfibrillar cellulose, NFC/MFC, and blends of two or more thereof.

4. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the barrier deposition coating is a vapour deposition coating of a material selected from metals, metal oxides, inorganic oxides and carbon coatings.

5. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the barrier deposition coating is an aluminium metallisation coating, which is applied to an optical density OD of from 1.8 to 2.5.

6. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the at least one gas barrier coating comprises a barrier dispersion coating, first applied by means dispersion or solution coating onto the ductile base layer pre-coating, and a barrier deposition coating, subsequently applied by a vapour deposition method, onto the barrier dispersion coating.

7. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the ductile base layer pre-coating is made from an aqueous composition comprising a polymer binder material having inherent ductility properties selected from the group consisting of styrene-butadiene copolymer latex, styrene acrylate copolymer latex, other latexes of acrylate polymers and copolymers, and of bio-based polymer materials.

8. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the ductile base layer pre-coating is made from an aqueous composition comprising a bio-based polymer binder material having inherent ductility properties selected from the group comprising starch derivatives, polyisoprene, lignin-based polymers, alginates, gums, and soy-based proteins and latexes of one or more such bio-based polymer binder material.

9. Barrier-coated cellulose-based substrate as claimed in claim 7, wherein the ductile base layer pre-coating further comprises a filler material.

10. Barrier-coated cellulose-based substrate as claimed in claim 7, wherein the ductile base layer pre-coating comprises from 4 to 45 wt % of the polymer binder material having inherent ductility properties, and from 55 to 96 wt % of a filler material, dry weight, and optionally further compounds, such as thickening agents and crosslinking compounds, at additive amounts.

11. Barrier-coated cellulose-based substrate as claimed in claim 7, wherein the ductile base layer pre-coating comprises per dry weight from 10 to 20 wt % of the polymer binder material having inherent ductility properties, from 75 to 85 wt-% of an inorganic filler, from 3 to 5 wt % of a crosslinking compound, and from 1 to 2 wt % of a thickening agent.

12. Barrier-coated cellulose-based substrate as claimed in claim 9, wherein the filler material is an inorganic laminar compound.

13. Barrier-coated cellulose-based substrate as claimed in claim 7, wherein the ductile base layer pre-coating has a grammage from 2 to 15 g/m.sup.2.

14. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the cellulose-based substrate has a second ductile coating on its opposite side.

15. Barrier-coated cellulose-based substrate as claimed in claim 9, having an ash content from 15 to 25 wt % as determined by ISO1762:2019.

16. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the cellulose-based substrate including the ductile base layer pre-coating, is calendered to an air permeance value lower than 100 nm/(Pa.Math.s) which is the lower limit of applicability of the test method ISO 5636-5:2013, and further lower than 1 nm as determined by SCAN-P 26:78.

17. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the cellulose-based substrate including the ductile base layer pre-coating and the at least one gas barrier coating, has a PPS surface roughness lower than 3.0 m as measured according to TAPPI 555 om-15, being the same as ISO 8791-4.

18. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the cellulose-based substrate comprises at least 50 wt % softwood cellulose.

19. Method of manufacturing a barrier-coated cellulose-based substrate as claimed in claim 1, which comprises a) a first step of providing a cellulose-based substrate, having a first side and a second side, as a moving web in a roll-to-roll system, b) a second step of applying a first aqueous dispersion of a ductile base layer pre-coating composition, onto the first side of the moving cellulose-based substrate, optionally applying a second aqueous dispersion of a ductile coating composition onto the other side of the moving substrate, and drying the applied ductile base layer pre-coating, and the optional second ductile coating composition, by forced evaporation, c) a third step of calendering the pre-coated and dried cellulose-based substrate from step b) to obtain a density of at least 900 kg/m.sup.3, and d) a fourth step of applying a gas barrier coating by means of dispersion coating a second aqueous dispersion or solution of a barrier composition, excluding nanocrystalline cellulose, NCC, onto the first side of the moving cellulose-based substrate and the ductile base layer pre-coating, and subsequently drying the applied barrier dispersion coating by forced evaporation, and/or by means of vapour depositing a barrier deposition coating onto the first side of the moving cellulose-based substrate with the ductile base layer pre-coating, to a total gas barrier coating thickness from 2 to 7000 nm.

20. Method as claimed in claim 19, wherein the first aqueous dispersion of the ductile base layer pre-coating composition is applied in the form of an aqueous composition comprising a polymer binder material having inherent ductility properties selected from the group consisting of styrene-butadiene copolymer latex, styrene acrylate copolymer latex, other latexes of acrylate polymers and copolymers, and of bio-based polymer materials.

21. Method as claimed in claim 19, wherein the first aqueous dispersion of the ductile base layer pre-coating composition further comprises a filler material.

22. Method as claimed in claim 19, wherein the pre-coated and dried cellulose-based substrate from step b) is calendered in the third step c) to obtain an air permeance value lower than 100 nm/(Pa.Math.s), which is the lower limit of applicability of the test method ISO 5636-5:2013, and further lower than 1 nm as determined by SCAN-P 26:78.

23. Method as claimed in claim 19, wherein in the third step c) the pre-coated and dried cellulose-based substrate from step b) is calendered to obtain a PPS surface roughness lower than 3.0 m as measured according to TAPPI 555 om-15, being the same as ISO 8791-4.

24. Method as claimed in claim 19, wherein the ductile base layer pre-coating is applied as an aqueous latex composition having a solids content from 48 to 51 wt %, and a Brookfield viscosity from 100 to 1000 mPa.Math.s, and a pH from 5.5 to 8.

25. Method as claimed in claim 19, wherein the pre-coated and dried cellulose-based substrate from step b) is super-calendered in step c).

26. Method as claimed in claim 25, wherein super-calendering is performed by from 3 to 8 roller nips at a nominal nip pressure of at least 100 KN and at a thermo-roller surface temperature from 100 to 300 C.

Description

EXAMPLES AND DESCRIPTION OF PREFERRED EMBODIMENTS

[0154] In the following, preferred embodiments of the invention will be described with reference to the drawings, of which:

[0155] FIGS. 1a and 1b schematically show in cross-section embodiments of barrier-coated cellulose-based substrates according to the invention,

[0156] FIG. 2a shows a schematic, cross-sectional view of an example of a laminated packaging material, comprising the barrier-coated cellulose-based substrate of FIG. 1a,

[0157] FIG. 2b is showing a schematic, cross-sectional view of a further example of a laminated packaging material comprising a barrier-coated cellulose-based substrate as of FIG. 1b,

[0158] FIG. 3a shows schematically a method, for dispersion coating a base layer or barrier pre-coating composition onto a cellulose-based substrate,

[0159] FIG. 3b shows schematically a method, for melt (co-) extrusion coating layer(s) of a thermoplastic heat sealable and liquid-tight polymer onto a web substrate, to form innermost and outermost layers of a packaging laminate of the invention,

[0160] FIG. 4a is showing a diagrammatic view of a plant for physical vapour deposition (PVD) coating, by using a solid metal evaporation piece, onto a substrate film,

[0161] FIG. 4b is showing a diagrammatic view of a plant for plasma enhanced chemical vapour deposition (PECVD) coating, by means of a magnetron plasma, onto a substrate film,

[0162] FIGS. 5a, 5b, 5c and 5d are showing typical examples of packaging containers produced from a laminated packaging material comprising a barrier-coated cellulose-based substrate according to the invention,

[0163] FIG. 6 is showing the principle of how such packaging containers are manufactured from the packaging laminate in a continuous, roll-fed, form, fill and seal process,

[0164] FIG. 7 is a diagram showing the effect of surface roughness on the oxygen transmission rate of different paper substrates, and

[0165] FIG. 8 shows schematically in cross-section an embodiment of a cellulose-based substrate pre-coated with a ductile base layer.

EXAMPLES

Example 1

[0166] Paper property characteristics were evaluated in laboratory scale to provide the most suitable cellulose-based substrate for this invention.

[0167] Table 1 below demonstrates the main properties used for selecting the most suitable paper substrate. Several paper structures were tested regarding their porosity (represented by Gurley air resistance), their mechanical resistance (represented by elongation and TEA-tensile energy absorption) and their surface smoothness (represented by Bendtsen and PPS roughness values) characteristics. The porosity of a paper can be measured either as an air resistance with the unit s/(100 ml) as determined by Tappi T460 om-02, or as an air permeance with the unit m/(Pa s), as determined by ISO5036-5:2013. For papers with very low porosity the air permeance, with the unit m/(Pa s), nm/(Pa s), or pm/(Pa s), is determined by SCAN-P 26:78.

[0168] Among the papers tested, the structures that presented the lowest porosity, with the highest Gurley air resistance value, at times not even detectable by the equipment due to a too high value, were papers 1, 2 and 11.

TABLE-US-00001 TABLE 1 Evaluated paper substrates with different porosity, mechanical resistance and surface roughness properties Roughness Paper (Bendtsen) Elongation Paper grammage (ml/m) PPS (m) Gurley (%) TEA (J/m.sup.2) Samples type (g/m.sup.2) Wire Felt Wire Felt (s/dl) MD CD MD CD A Paper 1 GPP 32 241.8 222.4 5.552 5.572 * 1.69 3.892 33.08 42.42 B Paper 2 GPP 58 391.6 336 * * * 2.456 3.932 86.42 80.34 E Paper 5 CP 45 156.3 184.2 4.774 4.475 41.29 2.232 7.638 78.55 123.52 F Paper 6 CP 60 8.4 9.4 1.358 1.442 9637 1.875 8.369 74.77 216.4 G Paper 7 CP 40 22.5 18.7 1.34 1.058 530.5 2.068 4.371 52.88 61.83 H Paper 8 NC 40 354.8 39.5 5.533 2.505 97.58 4.174 3.471 92.23 60.53 I Paper 9 NC 40 475.9 51.9 5.922 2.821 114.1 3.342 3.456 68.47 49.44 J Paper 10 CP 40 9.5 9.7 1.325 1.187 231.6 2.309 6.467 51.18 79.06 K Paper 11 CP 55 21 18 2.076 1.772 * 1.575 2.162 46.89 20.92 * Properties that exceeded the equipment's detection limit due to their high value. GPP means grease proof paper, CP means pre-coated paper and NC means non-coated paper.

[0169] The most suitable combination of the evaluated paper properties was found to be the one described under K in Table 1 above. In order to confirm that the structure was the most suitable for gas barrier application, the base layer pre-coating and the gas barrier coating formulations were applied to validate the oxygen transmission levels achieved with the selected paper base. The ductile base layer pre-coating and the barrier coatings were applied on the felt side, i.e. the top side, of the papers.

[0170] A summary of the analyses performed for coated papers is shown in Table 2. The surface roughness of the pre-coated papers was evaluated in PPS. The effect of the base layer pre-coating on the paper roughness represents the change (in %) of roughness, measured for coated papers, in comparison to the roughness measured for uncoated papers.

[0171] The paper substrates (A, B, F, G and K) were further coated with one or two layers of a nanocrystalline cellulose, NCC, gas barrier solution (total wet thickness of 25 m). The coatings were evaluated for coating weight, roughness, kit oil, grease resistance and oxygen barrier. Evaluation of these barrier coating properties indicates the effects of the type of base paper sheet and of its initial roughness on further gas barrier coating performance.

[0172] Kit oils were evaluated according to the Tappi T559 pm96 standard (KIT test). In this test, the organic solvent mixture is dropped onto the surface of the coated papers, followed by inspecting whether the organic solvents have penetrated the barrier layer and are absorbed by the paper. For this evaluation, grade 7-12 KIT test mixtures were used.

[0173] Oxygen barrier properties for Table 2 were evaluated according to ASTM D3985 and F1927-50 standards, using a MOCON sensor instrument, Ox-Tran model 2/22. Measurements were taken at 23 C. and 70% relative humidity 1 atm, i.e. 100% oxygen. For papers with higher initial surface roughness, OTR was measured after applying 2 coating layers (due to the failure of 1 layer to form a good barrier). For papers with low surface roughness, samples with 1 coating layer were evaluated (due to good barrier formation).

TABLE-US-00002 TABLE 2 Summary of analyses performed for coated papers selected for barrier application Number of Dry Grease Rougness gas barrier Roughness coating Effect of resistance OTR @ PPS, m, coating PPS, m weight, coating on KIT after 70% RH, Paper uncoated layers (coated) g/m.sup.2 roughness, % rating creasing ml/m.sup.2/day A 5.572 2 4.11 9.17 38.7 12 Yes 9.72 B * 2 6.99 9.8 13.8 12 Yes 35.06 F 1.442 1 1.50 4.18 +5.6 12 No 30.5 G 1.058 1 1.78 5.08 +14.8 12 Yes 3.06 K 1.772 1 2.66 5.5 +10.4 12 Yes 3.42

[0174] The effect of roughness on the oxygen transmission rate of barrier-coated papers is shown in FIG. 7.

[0175] As shown in Table 2 and as observed, surface roughness of the substrate paper has a substantial effect on the final barrier performance after coating. First, the higher the surface roughness of the base paper, the greater weight of the applied gas barrier coating is needed, although even when wet, greater thicknesses were applied to the different papers. This can be seen for paper A and B, which have relatively high surface roughness and consequently required high gas barrier coating weights. Also, on papers with higher roughness measurements, usually >3 m (PPS) as observed for A and B, the NCC coating barrier solution reduced the roughness of the paper. For papers with low surface roughness, there is a slight increase in roughness, but in terms of m, the roughness remains very low.

[0176] Secondly, as can be seen in Table 2 and FIG. 7, the lower the roughness of the base paper (usually <3 m), the better the barrier performance will be after barrier application. For paper structures such as G and K, with low roughness, it can be seen that only one coating layer was sufficient to achieve excellent oxygen and grease barriers, while for papers A and B, an insufficient oxygen barrier was achieved, although a high coating weight was applied. This implies that not only is barrier performance improved, but the number of layers needed to form the barrier is also decreased. After testing the grease resistance of the papers, all papers demonstrated an excellent grease barrier (KIT 12). Moreover, all papers except paper F demonstrated grease resistance after creasing of the paper. It seems that the roughness of paper has lower effect on the grease barrier compared to the oxygen barrier.

[0177] The performance of paper F was different from the other papers tested. At low roughness, paper F showed insufficient barrier performance in terms of oxygen transmission and grease resistance. Based on the properties of Paper K, combining a low surface roughness with low porosity, and providing good oxygen barrier properties, it may be concluded that not only the roughness affects the performance of the barrier, but also the composition of the paper, i.e. its porosity, and the composition of its surface.

[0178] Paper surface roughness is a very important parameter that will affect the effectiveness of the coated barrier layer, in terms of number of layers applied, weight of coating applied and barrier performance. A PPS roughness value lower than 3 m is required to be able to coat with just one layer and achieve good barrier performance. Surface roughness is not the only important parameter to consider, as each paper's composition and resistance properties can also affect performance.

[0179] Therefore, after studying and evaluating all the paper substrate structures described above and considering the combination of paper air resistance, i.e. porosity, surface roughness properties and the paper's performance in barrier tests after application on paper, the paper structure named as K was chosen as the most suitable structure to continue the scale-up studies and to design a proof-of-concept for validation of barrier performance.

[0180] Paper K is pre-coated and supercalendered, having a density above 1100 kg/m.sup.3 and is produced from 100% softwood Kraft pulp.

Example 2

[0181] The pre-coated high-density paper K is pre-coated on both sides, has a grammage of 55 g/m.sup.2 and all of its content is repulpable. FIG. 8 represents the structure of the pre-coated thin paper K, determined to be the best combination to ensure performance of further gas barrier coatings coated onto its top surface. The structure shown in FIG. 8 has ductile coatings applied to the surfaces of the top side as well as the bottom side of the paper, which will be described below. These ductile base layer coatings allow for optimal combination of low porosity and roughness to achieve the expected oxygen barrier performance. The ductile base layer pre-coating is applied directly onto the paper fibers. Directly on top of the heaviest layer on the top side (or felt side) of the paper (B in FIG. 8), the gas barrier coating is to be applied, in a later step.

[0182] The fiber composition represented as A in FIG. 8, is formed only from cellulose pulp fibers. These fibers are from bleached kraft softwood fibers and may have a grammage of 30 to 50 g/m.sup.2. The grammage of the coated paper will then be from 40 to 65 g/m.sup.2. The base paper for paper K has an uncoated grammage of 35 g/m.sup.2 and a ductile, pre-coated grammage of 55 g/m.sup.2.

[0183] The top and bottom surfaces of the fibrous composition A, were thus coated with aqueous pre-coatings of ductile dispersion compositions. These coatings had a pH of 5.5 to 8, solid content of 48 to 51%, Brookfield viscosity of 100 to 1000 mPa.Math.s, while the coated material exhibits a Tg ranging from 30 to 0 and 0 to 30 ( C.), and may described in terms of chemical composition as an aqueous dispersion of a styrene-butadiene binder copolymer, a so-called SB-latex, and a kaolin clay filler. The pre-coating composition used comprised about 15 wt % of SB-latex, about 80 wt % of kaolin filler material, about 4 wt % crosslinking starch compound and further additives, such as less than 2 wt % of a thickening agent.

[0184] As illustrated in FIG. 8, the coating layer B applied onto the paper top side may have a weight of 5 to 15 g/m.sup.2, such as from 10 to 15 g/m.sup.2, applied as a single layer. The coating composition illustrated in C, applied onto the bottom/back of the paper, may have a grammage from 1 to 10 g/m.sup.2 applied in a single layer and is also obtained from an aqueous dispersion comprising a styrene-butadiene copolymer and kaolin. The coated paper as illustrated by the set of A, B and C may thus have a final grammage between 40-65 g/m.sup.2.

[0185] The thus pre-coated paper K as illustrated in FIG. 8, with layers A, B and C had a grammage of 55 g/m.sup.2 and final porosity lower than 100 nm/(Pa s) as determined by ISO5636-5:2013, which is the lower limit of the applicable range of the test method, and further lower than 1 nm, as determined by SCAN-P 26:78. The pre-coated paper had a PPS roughness lower than 2 m, i.e. about 1.8 m, on its top side. The final, NCC gas-barrier-coated paper K as of Table 2 exhibited a felt side surface roughness of about 2.8. Thus, the pre-coated and barrier-coated paper of the invention may have a PPS surface roughness of lower than 3 m, such as from 0.5 to 3 m.

Example 3

[0186] Mechanical resistance properties of the pre-coated cellulose-based substrates used were explored to demonstrate the importance and contribution of each layer of the pre-coated paper composition to the final application of the barrier-coated substrates.

[0187] Material failure by nucleation and propagation of a crack in the substrate will create openings and discontinuities in the barrier coating layer, thus destroying the final package barrier. The more elongation the substrate can undergo before failure the more resilient is the substrate to various loads, such as bending during package forming. By becoming more flexible, the structure after pre-coating with a ductile material and subsequent drying and calendering, allows the pre-coated paper structure to more effectively resist bending and the initiation of breaks in its surface.

[0188] This behavior of reduced stiffness of the structure containing cellulose fibers and the top and backside coatings after calendering can be illustrated with the reduction of Young's Modulus as shown in tables 3 and 4, in both MD and CD directions of the paper. The reduction in Young's Modulus means that the stiffness of the total material structure decreases, which allows the material to gain more flexibility and thus become more resilient and resistant to creasing and folding processes.

[0189] The application of the flexible or ductile base layer pre-coating on the fibrous layer allows for a gain in ductility of the final material, which will result in a material more resistant to breakage, cracking and damage in the process of converting a package.

TABLE-US-00003 TABLE 3 Average of the values obtained for the stress strain curves of each pre-coated paper layer material described in FIG. 7 (i.e. A B F G K), as well as the influence of the individual coating layers on final ductility of each of the materials in the MD direction of the paper Description of the layer Elongation Energy at Breaking Layer or and surface Maximum at Max. Maximum Point Modulus structure treatment Load [N] load [mm] Load [J] Load [N] [MPa] A 100% fiber layer 20.58 0.30 0.005 7.55 2418.7 BAC A pre-coated on 18.05 0.32 0.004 6.19 1648.3 both sides BAC BAC structure 14.60 0.42 0.005 7.85 1269.0 after calendering

TABLE-US-00004 TABLE 4 Average of the values obtained for the stress strain curves of each pre-coated paper layer material described in FIG. 7 (i.e. A B F G K), as well as the influence of the individual coating layers on final ductility of the materials in the CD direction of the paper Description of the layer Elongation Energy at Breaking Layer or and surface Maximum at Max. Maximum Point Modulus composition treatment Load [N] load [mm] Load [J] Load [N] [MPa] A 100% fiber layer 15.00 0.62 0.007 2.99 1108.4 BAC A pre-coated on 14.94 0.85 0.010 4.35 862.5 both sides BAC BAC structure 14.20 0.98 0.010 4.61 634.7 after calendering

[0190] The mechanical resistance properties of the pre-coated and uncoated papers evaluated here, when in conjunction with the laboratory barrier application exploration results, provide an understanding of the excellent performance achieved. For example, the elongation at maximal load increases as the cellulose-based substrate or paper is pre-coated (measurements B) and further as the pre-coated paper is calendered (measurements C). This confirms the beneficial effect of providing a more ductile/flexible material as substrate for the gas barrier, so that the gas barrier coated substrate can withstand higher elongation without cracking during conversion of packaging material into packages.

Example 4

[0191] The invention described herein, in addition to bringing unique features that allow for reaching high oxygen barrier levels, is therefore a solution capable of replacing non-renewable components in packaging, has high content of renewable materials, and is 100% repulpable or recyclable according to the PTS RH 021/97 standard.

[0192] For recycling the thin, ductile, pre-coated paper substrate selected for the application developed here, in addition to the performance of repulpability tests according to PTS RH 021/97, a repulpability study was also performed in the laboratory.

[0193] To evaluate repulpability in the laboratory, a sample of known weight of paper was dispersed at 23 C. using a device with capacity of 3000 revolutions/min, for 20 minutes of agitation. After the 3rd minute of stirring, it was already possible to see that the paper is repulpable. No lumps were detected in the water suspension, indicating that the paper was already dispersed in the water.

Example 5

[0194] A gas barrier coating formulation based on NCC was used for coating the flexible pre-coated paper substrate, which can be characterized as containing 5 to 22% solids, and having a viscosity of 600 to 25002 mPa.Math.s. The chemical components of the formulation were based on NCC (CNC), PVOH and starch-based materials and contained at least 50% of the renewable materials (NCC and starch), such as at least 50% of NCC, and is 100% recyclable and biodegradable.

[0195] Nanocelluloses have challenging rheologies, so when added to blends with other polymers and components, they cause a change in rheology by altering the final viscosity of the suspension. NCCs (Nanocrystalline Cellulose or Cellulose Nanocrystals) are extracted from hardwood or softwood cellulosic pulp, and all of their dimensions are on the nanometric scale. The NCCs used have all their dimensions on the nanometric scale, with widths ranging from 5 to 20 nm and lengths from 150 to 400 nm.

[0196] A double layer gas barrier layer of nanocrystalline cellulose or PVOH or other gas barrier material may be formed on the top side surface of the ductile pre-coated paper. A first gas barrier coating creates a gas barrier layer onto the ductile base layer pre-coating of the top side of the paper, and a second gas barrier coating provides a second gas barrier layer onto the first gas barrier coating layer.

[0197] The sequence of barrier layer application is essential in this case, onto the ductile pre-coated paper. The first gas barrier dispersion layer is applied onto the ductile base layer pre-coating on the top side surface of the paper, by means of bar coating, and this layer is dried using infrared and hot air to form a homogeneous gas barrier layer on the surface. The application speed used in the tests was 300 to 600 m/min to ensure good quality of gas barrier coating layers formed on the ductile pre-coated paper surface. The first formed gas barrier dispersion layer prepares the surface to receive the second barrier dispersion layer, which is also formed by means of bar coating, onto the dried first barrier dispersion layer. The second gas barrier dispersion layer applied also goes through a process of film forming and drying using infrared and hot air for drying. It should be noted that the optimal range for drying using hot air tested for the formulation and the ductile pre-coated paper is from 90 to 150 C.

[0198] Drying at evaluated temperatures does not cause loss of barrier levels, and provides good formation of a coating film on the pre-coated paper surface, even at higher temperatures. Finally, to ensure proper winding and cooling of the barrier-coated paper substrate, after drying, the coated paper should be rolled at temperatures below 40 C. This secures the formation of a homogenous film, ensuring high oxygen- and grease-barrier performance.

Example 6

[0199] Different conditions were tested for larger scale application of a gas barrier coating on the surface of paper K, described above. The gas barrier coating was applied on a pilot coating machine that allowed for using different technologies, however, bar or blade coating methods were the application technologies used to form the gas barrier coating layers applied onto the ductile pre-coating B, as illustrated in FIG. 8, with a total dry coating amount of from 0.5 to 5 g/m.sup.2. Application bars are smooth, and their diameters can vary, here bar diameters from 18 to 30 mm were used. The tests were made by applying the gas barrier directly onto the ductile pre-coated base paper as illustrated in FIG. 8.

[0200] In a final prototype for proof-of-concept and upscaling, the characteristics of the ductile pre-coated papers used in the development were as described in Table 5 below.

TABLE-US-00005 TABLE 5 Characteristics of the paper used in large-scale test Paper Paper Layer B Layer C PPS top PPS bottom SCAN-P Paper thickness density coating coating layer layer 26:78 Tests (g/m.sup.2) (m) (kg/m.sup.3) (g/m.sup.2) (g/m.sup.2) (m) (m) (pm/Pa .Math. s) Large- 55-60 45-50 1222-1333 12-15 5 2.07 2.1 206 scale Proto- type

[0201] In this upscaling work, it was thus seen that pre-coated paper substrates having a lower surface roughness and a lower porosity generally provided better results and provided improved oxygen barrier levels in formed and filled packages.

[0202] The barrier formulation containing NCC was thus applied onto the ductile pre-coating B on the top side of the paper substrate A (FIG. 8), i.e. onto the top surface with the highest pre-coating weight, by forming a 2-layer gas barrier coating of 22.5 g/m.sup.2 of NCC, resulting in package OTR 21% O.sub.2 (cc/pkg/24 h) of 0.016 at 0.2 atm and 50% RH, according to ASTM F1307-14.

[0203] The aqueous dispersion containing cellulose nanocrystals was thus applied to surface B in a first step, thereby consolidating a final gas barrier layer measuring about 2.5 g/m.sup.2, which prepared the surface to receive the second gas barrier dispersion coating layer. After applying the first layer, it is dried by infrared heating and hot air convection. A second layer measuring about 2.5 g/m.sup.2 was applied onto the first gas barrier coating, to form a total 2-layer gas barrier coating of about 5 g/m.sup.2. After applying the second layer, it is dried by infrared heating and hot air, and finally, the solidified resin is cooled to a temperature below 40 C., to prevent bonding between sheets of paper with a barrier already applied on the surface (bonding the sheets with the still active, uncooled resin).

[0204] The amount applied was limited to 2.5 g/m.sup.2 for each part-layer, to prevent excess water on the cellulose-based substrate. Using the pre-coated paper as described in FIG. 7 allows for greater dimensional stability control as the flexible pre-coating B acts as a surface preparer as well as impacting the surface roughness and porosity of the substrate.

[0205] The application technology used for forming this gas barrier coating was a bar coating method. A bar diameter of 24 mm was used. The bar used for applying the barrier dispersion was rotating in the same direction as the paper winding with speed from 20 to 80 rpm, or in the opposite direction to the paper winding direction with speed from 80 to 160 rpm.

Example 7

[0206] The paper substrate K from Table 1, as well as the previously best tested substrate paper type for carrying oxygen barrier coatings, i.e. a Superperga WS 32 gsm Parchment FL109 greaseproof paper from Nordic Paper, were for comparison (Comparative Example 1), laminated in the same way with LDPE on their respective top sides at 20 g/m.sup.2.

[0207] The comparative paper was measured to have a surface roughness on the top side, i.e. the side to be barrier-coated, of about 36 ml/min Bendtsen. It comprised cellulose refined to a higher degree, i.e. cellulose of smaller fibrous/fibrillar molecules, to provide its dense surface and medium paper density of merely 865 kg/m.sup.3. The comparative paper is not 100% recyclable, but leaves a reject of water-swollen, low-molecular cellulose.

[0208] The paper substrate K used in the invention had a top side Bendtsen roughness of about 20 ml/min.

[0209] The oxygen transmission rates through the flat laminated papers of Example 1 and Comparative Example 1 were measured using a coulometric detector and the evaluation was done according to ASTM F1927-14 by the unit cm.sup.3/m.sup.2/24 h at 0.2 atm oxygen pressure and a moisture level of 50% relative humidity. The results from the measurements are presented in Table 6.

TABLE-US-00006 TABLE 6 OTR for flat papers laminated with PE, cm.sup.3/m.sup.2/24 h at 0.2 atm, 50% RH Comparative Example 1: Example 1: Superperga WS 32 g/m.sup.2 Pre-coated Parchment FL109 GPP paper Highly refined grease- High-density (super- proof paper, with a calendered) and ductile density of 865 base layer pre-coated Paper kg/m.sup.3 Sulphate SW paper Flat paper OTR 0.2 42 71 atm, 23 C., 50% RH

[0210] From the results in Table 6, it is seen that the best previously studied paper substrate as a laminated sample provides better initial, inherent OTR performance than the base layer pre-coated paper substrate of the invention.

[0211] The pre-coated paper substrates from Example 7 but without the laminated layers of LDPE on both sides, were thus instead coated with a first gas barrier coating of polyvinyl alcohol, PVOH, or NCC, respectively, onto the ductile base layer pre-coating (top side of paper substrate). The PVOH used was obtained from Kuraray and had a degree of hydrolysis of at least 98%, i.e. Poval 6-98. The dispersion of PVOH was applied by means of a smooth roller coating method in pilot-scale equipment, and the wet amount applied of the aqueous dispersion of the PVOH was about 15 weight-%. For the purpose of anti-foaming, 0.05 volume-% of 1-octanol was added to the PVOH. The Brookfield viscosity at 23 C. of the PVOH dispersion barrier composition was 500-800 mPa.Math.s.

[0212] The rotation speed of the coating roller was 160 rpm, with rotation in opposite direction compared to the web running direction. The coating was applied in two steps, with a dry grammage of the first and second layer of 1.6 g/m.sup.2 and 1.6 g/m.sup.2, respectively.

[0213] A combination of infrared irradiation IR and hot air was used for drying the coated layers and the surface temperature was kept at below 100 degrees Celcius while the web speed was about 300 m/min during coating.

[0214] In a different coating operation in the same pilot-scale equipment, a dispersion of NCC was instead applied, by means of a smooth roller coating method. The amount applied of the aqueous dispersion of the NCC was about 19-20 weight-%. The Brookfield viscosity at 23 C. of the aqueous NCC dispersion barrier composition was <2000 mPa.Math.s and the viscosity at 50 C. was 1000-1200 mPa.Math.s. Both IR and hot air was used for drying the coated layers and the web speed was about 300 m/min during coating. The rotation speed of the coating roller was 80 rpm, with rotation in opposite direction compared to the web running direction. The coating was applied in two steps, with a dry grammage of the first and second layer of 1.9 g/m.sup.2 and 2.7 g/m.sup.2, respectively.

[0215] The pre-coated and gas-barrier coated papers were then laminated with 20 g/m.sup.2 LDPE on its top sides and the oxygen transmission rates were evaluated as for Example 7 and for Comparative example 1, but also including 80% moisture level. The oxygen transmission rates are shown in Table 7.

TABLE-US-00007 TABLE 7 OTR for pre-coated and barrier-coated papers laminated with PE. PVOH NCC 4.6 3.2 gsm gsm Flat paper OTR 0.2 atm, 0.31 0.13 23 C., 50% RH Flat paper OTR 0.2 atm, 7.93 17.2 23 C., 80% RH

[0216] From the results in Table 7, it is seen that the OTR performance of the pre-coated and barrier-coated paper is significantly improved compared to the pre-coated paper without a gas barrier coating in Table 6. Both the PVOH coating and NCC coating improves the OTR performance. It is however noted that both types of coating are sensitive to moisture, with higher OTR for 80% RH compared to OTR at 50% RH.

Example 8

[0217] The pre-coated and gas-barrier dispersion-coated papers from Example 7 were metalized to an optical density of about 1.8. The metalized barrier papers were then extrusion coating laminated with paperboard and polymers to provide a packaging material according to the following structure: [0218] //Outside 12 g/m.sup.2 LDPE/Duplex CLC 80 mN, 200 g/m.sup.2, paperboard bulk layer/LDPE 20 g/m.sup.2 bonding layer/barrier-coated paper substrate [0219] (with 2 barrier coating 4 g/m.sup.2/Al metal OD1.8/Adhesive layer EAA copolymer 6 g/m.sup.2/blend LDPE+m-LLDPE 29 g/m.sup.2//

[0220] The liquid paperboard was prior to lamination creased to facilitate sub-sequent folding of packages. Lamination of the packaging material was carried out in a flexible pilot laminator with three extrusion coating stations. The lamination speed was about 400 m/min.

[0221] The Duplex CLC paperboard was a clay-coated paperboard of the conventional type, and the m-LLDPE is a metallocene-catalysed linear low density polyethylene. The barrier-coated side of the paper substrate was directed in the laminated structure towards the inside (corresponding to the inside of a packaging container manufactured from the laminated material). The adhesive polymer EAA and the innermost heat-sealable layer were coextrusion coated together onto the barrier-coated paper and the outermost layer of LDPE was extrusion coated onto the outside of the paperboard.

[0222] The oxygen transmission rates through the flat laminated packaging materials of Example 8 were measured using a coulometric detector and the evaluation was done according to ASTM F1927-14 by the unit cm.sup.3/m.sup.2/24 h at 0.2 atm oxygen pressure and at moisture levels of 50% and 80% relative humidity.

Comparative Example 2

[0223] The previously tested paper substrate also used in Comparative Example 1, was gas-barrier coated and laminated into a packaging material structure in a substantially corresponding way, except for the ductile base layer pre-coating not being included.

[0224] The paper was first coated in two consecutive dispersion coating operations with 1.5 g/m.sup.2 each of PVOH (Poval 15-99, fully saponified PVOH), with drying after each step. Then it was metallised to an optical density of about 2.3.

[0225] The barrier-coated comparative paper substrate was further laminated into a packaging material structure as follows: [0226] //Outside 12 g/m.sup.2 LDPE/Duplex CLC 80 mN, 200 g/m.sup.2, paperboard bulk layer/LDPE 20 g/m.sup.2 bonding layer/barrier-coated paper substrate [0227] (with 2 barrier coating 1.5 g/m.sup.2/Al metal OD2.3/Adhesive layer EAA copolymer 6 g/m.sup.2/blend LDPE+m-LLDPE 19 g/m.sup.2//

[0228] The results of OTR measurements on the laminated packaging materials of Example 8 and Comparative Example 2 are presented in Table 8.

TABLE-US-00008 TABLE 8 OTR for flat laminated packaging materials Comparative Example 8-1: Example 8-2: Example: Pre-coated Pre-coated Superperga WS paper paper with 32 g/m.sup.2 with NCC PVOH Parchment barrier barrier FL109 GPP coating coating Laminate structure: 80 mN 80 mN 80 mN /LDPE/paperboard paperboard 1.5 paperboard 4.6 paperboard 3.2 /LDPE/paper + g/m.sup.2 PVOH; Met g/m.sup.2 NCC; Met g/m.sup.2 PVOH; pre-coating + to OD ~2.3 to OD ~1.8 Met to OD ~1.8 barrier coating + met/inside PE polymers/ Flat laminate OTR 1.3* 1 atm, 23 C., 50% RH Flat laminate OTR 1.3* 1 atm, 23 C., 80% RH Flat laminate OTR 0.26** 0.39* 0.38* 0.2 atm, 23 C., 50% RH Flat laminate OTR 0.26** 0.38* 0.36* 0.2 atm, 23 C., 80% RH *Measured at oxygen pressure 1 atm/0.2 atm **Converted to oxygen pressure 0.2 atm

General

[0229] It can be seen in Table 8 that the OTR values for packaging material using a pre-coated and barrier coated paper are higher than for packaging material using a highly refined grease-proof paper, even though the barrier coating grammages were higher on the pre-coated paper of the invention. This can be attributed to that the OTR contribution from the paper itself is lower for the pre-coated paper compared to the highly refined grease-proof paper, see Table 7.

[0230] It is also noted that the packaging material using pre-coated and barrier coated paper are not sensitive to an increased moisture level.

Example 9

[0231] Packages were produced in a Tetra Pak E3/CompactFlex filling machine. This type of filling machine has the capacity to fill portion packages at a speed of 9000 packages/hour and a flexibility that allows for quick change between different package formats. Packages were in the format of Tetra Brik with a volume of 200 ml.

[0232] The Oxygen transmission rate of packages (filled, emptied and dried) was measured with packages mounted on a special holder; inside the package nitrogen is purged; the outside of the package is exposed to the environment surrounding the instrument. When oxygen permeates through the package into the nitrogen carrier gas, it is transported to the coulometric sensor. The sensor reads how much oxygen that leaks into the nitrogen gas inside the package. OTR is then evaluated according to ASTM F1307-14, at 0.2 atm (surrounding air containing 21% oxygen). The measurement unit is cm3/package/24 h.

TABLE-US-00009 TABLE 9 OTR for including loss factors. Comparative Example 8-1: Example 8-2: Example 2: Pre-coated Pre-coated Superperga WS paper with paper with 32 gsm NCC PVOH Packaging material Parchment barrier barrier used FL109 GPP coating coating Package format Tetra Brik Tetra Brik Tetra Brik Aseptic 200S Aseptic 200S Aseptic 200S Package volume 200 ml 200 ml 200 ml Laminate area per 0.030 m.sup.2 0.030 m.sup.2 0.030 m.sup.2 package Calculated, 0.0078 0.0117 0.0114 theoretical* OTR per package, 0.2 atm, 23 C., 50% RH Measured OTR per 0.075 0.016 0.013 package 0.2 atm, 23 C., 50% RH Loss factor 9.6 1.4 1.1 measured/theoretical, 23 C., 50% RH *Using the package laminate area and the corresponding OTR value for flat packaging material in Table 2.

[0233] It is interestingly noted from Table 9, and surprisingly too, that even though the OTR values for flat laminated packaging materials using pre-coated and barrier coated paper are higher than for flat laminated packaging materials using a highly refined grease-proof paper, as seen from Table 7, the package OTR values are improved by using the pre-coated and barrier coated paper. The measured package OTR is 0.013-0.016 cm.sup.3/package/24h/0.2 atm instead of 0.075. When dividing the measured OTR values with the corresponding theoretically calculated ones it is also seen that the loss factors are close to 1 when using pre-coated and barrier coated paper, compared to a loss factor of 9.6 when using a highly refined grease-proof paper. It is evident that the gas barrier performance on the flat laminated packaging material is preserved even after folding of the packages, when using pre-coated and barrier coated paper. This is attributed to the ductile base layer pre-coating, which is able to reduce the effect of stress concentrations in the paper. Stress concentrations are otherwise an origin for cracks to initiate and propagate through the paper. If the paper cracks, a very thin barrier coating is not able to withstand the high stress and will consequently also crack, thus imparting the gas barrier. Ductile materials in particular, are able to withstand high strain and being able to re-distribute the stress concentrations in the paper during folding.

[0234] Further, relating to the attached figures:

[0235] In FIG. 1a, there is shown, in cross-section, an embodiment of a barrier-coated cellulose-based substrate 10a, of the invention. The substrate 11a is a paper made from a major proportion of cellulose fibers from sulphate softwood pulp, having a grammage of 35 g/m.sup.2, first provided with a ductile base layer pre-coating 12a on its top side, by applying a latex or biopolymer binder composition, such as specifically in this example an SB-latex binder composition further also comprising an inorganic laminar filler material, by means of aqueous dispersion coating and subsequent drying to evaporate the water. The dry weight of the applied ductile base layer pre-coating is about 12 g/m.sup.2. Optionally, a further, second, ductile coating 15a, of the same composition as the ductile base layer pre-coating 12a, may be applied in the same manner onto the opposite, uncoated side of the paper substrate 11a. The dry weight of the, second, ductile coating is about 5 g/m.sup.2. The thus pre-coated paper substrate is subsequently super-calendered by passing several high pressure roller nips and at least one thermoroll applying a surface temperature of from 100 to 240 C.

[0236] Further, the paper substrate has a gas barrier coating 13a made from a barrier dispersion or solution coating of PVOH, Poval 6-98 from Kuraray, applied onto the surface of the ductile base layer pre-coating 12a. The gas barrier coating 13a is thus applied by means of aqueous dispersion coating and subsequently dried to evaporate the water, preferably as two consecutive part-coating steps with drying in between and after. The total dry weight of the PVOH barrier dispersion coating is about 3.5 g/m.sup.2. Further and optionally, the barrier dispersion-coated paper substrate may have an aluminium barrier deposition coating 14a, i.e. an aluminium-metallised layer, applied onto the dried surface of the barrier dispersion coating 13a, and by physical vapour deposition to an OD of about 1.8.

[0237] FIG. 1b shows, in cross-section, a further embodiment of a barrier-coated cellulose-based substrate 10b, of the invention. The same paper is used as the cellulose-based substrate as in FIG. 1a, and is coated with a first ductile, base layer pre-coating 12b of the same composition as used in FIG. 1a, at a dry weight amount of about 12 g/m.sup.2. A further, second, ductile coating 15b, of the same composition as the ductile base layer pre-coating 12b, is applied in the same manner onto the opposite, uncoated side of the paper substrate 11b. The dry weight of the second, ductile coating is about 5 g/m.sup.2.

[0238] In this embodiment, there is no gas barrier dispersion coating applied, but the first ductile base-layer pre-coating 12b is directly coated with a gas barrier deposition coating 14b of an aluminium-metallised layer, to an OD of about 2. The second, ductile coating 15b is, on the other hand, coated with a gas barrier coating 13b made from a barrier dispersion or solution coating of PVOH, Poval 6-98 from Kuraray, as described in FIG. 1a. The total dry weight of the PVOH barrier dispersion coating is about 3.5 g/m.sup.2. The resulting barrier-coated paper substrate thus has one gas barrier coating applied on each side of the paper, each with a ductile coating beneath it, as a bridging layer between the surface of the paper substrate and the respective gas barrier coating, 14b and 13b.

[0239] In FIG. 2a, a laminated packaging material 20a for liquid carton packaging is shown, in which the laminated material comprises a paperboard bulk layer 21a of paperboard, having a bending force of 80 mN and a grammage weight of about 200 g/m.sup.2, and further comprising an outer liquid tight and heat sealable layer 22a of low density polyethylene applied on the outside of the bulk layer 21a, which side is to be directed towards the outside of a packaging container produced from the packaging laminate. The layer 22a is transparent to show the printed decor pattern 27a, applied onto the bulk layer of paper or paperboard, to the outside, thus informing about the contents of the package, the packaging brand and other information targeting consumers in retail facilities and food shops. The polyethylene of the outer layer 22a is a conventional low density polyethylene (LDPE) of a heat sealable quality, but could also include further similar polymers, including LLDPEs. It is applied at an amount of about 12 g/m.sup.2. An innermost liquid tight and heat sealable layer 23a is arranged on the opposite side of the bulk layer 21a, which is to be directed towards the inside of a packaging container produced from the packaging laminate, i.e. the layer 23a will be in direct contact with the packaged product. The thus innermost heat sealable layer 23a, which is to form strong transversal heat seals of a liquid packaging container made from the laminated packaging material, comprises one or more in combination of polyethylenes selected from the groups consisting of LDPE, linear low density polyethylene (LLDPE), and LLDPE produced by polymerising an ethylene monomer with a C4-C8, more preferably a C6-C8, alpha-olefin alkylene monomer in the presence of a metallocene catalyst, i.e. a so called metalloceneLLDPE (m-LLDPE). This innermost layer of polyethylenes is applied at an amount of about 29 g/m.sup.2.

[0240] The bulk layer 21a is laminated to the uncoated side (i.e. having no gas barrier coating applied) of the barrier-coated paper substrate 10a, from FIG. 1a, i.e. 25a, having also an aluminium barrier deposition coating 14a, i.e. an aluminium-metallised layer, applied onto the dried surface of the barrier dispersion coating 13a, by physical vapour deposition to an OD of about 1.8, by an intermediate bonding layer 26a of a low density polyethylene (LDPE). The intermediate bonding layer 26a is formed by means of melt extruding it as a thin polymer melt curtain between the two paper webs and thus laminating the bulk layer and the barrier-coated paper substrate to each other, as all three layers pass through a cooled press roller nip. The amount applied of the intermediate bonding layer 26a is about 20 g/m.sup.2.

[0241] The innermost heat sealable layer 23a may consist of one layer or alternatively of two or more part-layers of the same or different kinds of LDPE or LLDPE or blends thereof, and is well adhered to the metallised barrier deposition coating surface 14a of the barrier-coated paper substrate 10a, by an intermediate coextruded tie layer 24a at an amount of about 6 g/m.sup.2, e.g. of ethylene acrylic acid copolymer (EAA), which thus bonds the innermost heat sealable layer(s) to the barrier coated paper substrate 10a, by applying the layers together in one single melt coextrusion coating step of layers 24a and 23a.

[0242] In order to reduce the amount of the thermoplastic polymer fraction in recycling processes, such as extrusion laminated polyethylene polymers, and for improved repulpability of the packaging material in recycling processes, the lamination layer 26a, which is bonding the barrier-coated cellulose-based substrate 25a to the bulk layer 21a, may be a thin layer of a wet laminated polymer binder instead, obtained from drying of a dispersion-coated aqueous adhesive composition. Such a lamination step is performed in an efficient cold or ambient lamination step at industrial speed without any energy-consuming drying operation needed to accelerate the evaporation of the water. The dry weight of such a bonding layer would in such an embodiment only need to be about 6 g/m.sup.2, or preferably lower, and be made from a polymer which is readily re-dispersible in water such that it is repulpable into the fraction of cellulose fibres in a carton fibre recycling process.

[0243] In a further embodiment, the back-side of the paper substrate 11a may first be coated with a second, ductile coating 15a, of the same or a similar composition as the ductile base layer pre-coating 12a, at a dry weight of about 5 g/m.sup.2, as described in connection to FIG. 1a, and then the bonding layer 26a may comprise a similar aqueous adhesive composition as the ductile base layer pre-coating composition 15a. In a different embodiment, the paper substrate 11a may remain uncoated on the backside, while the amount of such bonding layer 26a may be higher, such as from 10 to about 12 g/m.sup.2, to simultaneously produce one single layer 26a, behaving both as a ductile base layer 15a and a lamination bonding layer 26a.

[0244] Alternatively, a bulk layer 21a may be laminated to the uncoated side (i.e. having no gas barrier coating applied) of a barrier-coated paper substrate 10a, from FIG. 1a, however not having the optional aluminium barrier deposition coating 14a, by the same methods as described above. On the inside of the barrier-coated barrier substrate there is instead laminated a pre-manufactured polymer film substrate having a barrier deposition coating, applied by means of a vapour deposition method, such as a metallisation coating laminated to the barrier-coated cellulose based substrate. The polymer film substrate may be laminated to the barrier-coated cellulose-based substrate by an interjacent bonding layer of a polymer, either by means of extrusion lamination of a thermoplastic bonding layer between the two barrier-coated webs, or by wet lamination of an aqueous adhesive. The metallised polymer film substrate may comprise a heat sealable material layer on the side of the polymer film substrate facing away from the metallisation coating, to form the second, innermost liquid-tight and heat sealable material layer. Alternatively, the metallised polymer film substrate may be further extrusion coated with the second, innermost liquid-tight and heat sealable material layer 23a. The layers and the materials and polymers are otherwise be the same as in the laminated packaging material of FIG. 2a, and described above.

[0245] In FIG. 2b, a different laminated packaging material 20b, for liquid carton packaging, is shown, in which the laminated material comprises a paperboard core layer 21b, having a bending force of 80 mN and a grammage weight of about 200 g/m.sup.2, and further comprises an outer liquid tight and heat sealable layer 22b of LDPE applied on the outside of the bulk layer 21b, as described in FIG. 2a. Furthermore, a similar innermost liquid tight and heat sealable layer 23b is arranged on the opposite side of the bulk layer 21b, as described above in FIG. 2a.

[0246] The bulk layer 21b is laminated to the barrier-coated paper substrate described in FIG. 1b, by means of wet lamination with an intermediate bonding layer 26b of a thin layer of adhesive polymer, obtained by applying an aqueous dispersion of a polyvinyl acetate adhesive, or a starch adhesive, onto one of the surfaces to be adhered to each other and subsequently pressing together in a roller nip. This lamination step is thus performed in an efficient cold or ambient lamination step at industrial speed without any energy-consuming drying operation needed to accelerate the evaporation of the water. The dry amount applied of the intermediate bonding layer 26b is from 3 to 5 g/m.sup.2 only, which entails that there is no need for drying and evaporation of the bonding layer.

[0247] Thus, the amount of thermoplastic polymer can be significantly reduced in this lamination layer, in comparison to the conventional melt extrusion laminated bonding layer of LDPE, described in FIG. 2a.

[0248] This resulting laminated packaging material 20b thus has a barrier-coated cellulose based substrate as described in FIG. 1b, having a gas barrier coating applied on each side, with the barrier deposition layer 14b, in this case the metallised layer, being directed towards the inside and the innermost layer 23b, and the barrier dispersion coating 13b directed towards the bulk layer 21b. Both gas barrier coatings 14b and 13b have each a ductile coating beneath it, acting as a flexible, cushioning layer 12b and 15b, respectively.

[0249] In yet further embodiments of either the laminated structure of FIG. 2a (not shown), or the laminated structure of FIG. 2b (not shown), the innermost liquid-tight layer 23a or 23b may consist of a pre-manufactured, blown film, comprising LDPE or LLDPE polymers in any blends thereof, and it may be laminated to the barrier-coated paper substrate, to the surface of its barrier deposition coating, i.e. the aluminium metallisation, by means of an intermediate, melt extrusion laminated bonding layer 24a or 24b, comprising a thicker tie layer of EAA than used in FIG. 2a or 2b, or a more simple bonding layer of LDPE, which is from 12 to 20 g/m.sup.2, such as from 12 to 18 g/m.sup.2, thick.

[0250] Alternatively, the pre-manufactured blown film 23a or 23b may be laminated to the metallised coating by means of another wet lamination bonding layer, of an aqueous adhesive of an acrylic (co) polymer adhesive layer 24a or 24b, at ambient (cold) temperature, at an amount from 3 to 5 g/m.sup.2. As stated above, if the barrier deposition coating 14a is not applied to the barrier-coated paper substrate, a barrier deposition coating may be applied to the pre-manufactured film instead, by vapour deposition coating.

[0251] In FIG. 3a, an embodiment of a principal process of aqueous dispersion coating 30a is shown, which may be used for applying a gas barrier coating 12 from an aqueous gas barrier composition onto a substrate, or for applying a ductile base layer pre-coating from an aqueous latex composition. Alternatively, it may be used for applying an aqueous adhesive composition for wet laminating two webs together, of which at least one web has a fibrous cellulose surface. The web of cellulose-based substrate 31a (e.g. the paper 11a, 11b from FIG. 1a, 1b) is forwarded to the dispersion coating station 32a, where the aqueous dispersion composition is applied by means of rollers onto the top surface of the substrate. The aqueous dispersion composition may have an aqueous content of from 80 to 99 weight-%,-%, in the case of barrier compositions, thus there may be a lot of water on the wet coated substrate that needs to be dried by heat, and evaporated off, to form a continuous coating, which is homogenous and has an even quality with respect to barrier properties and surface properties, i.e. evenness and wettability. The drying is carried out by a hot air dryer 33a, which also allows the moisture to evaporate and be removed from the surface of the substrate. The substrate temperature as it travels through the dryer, may be kept constant at a temperature of below 100 C., such as below 90 C., such as from 70 to 90 C., in order to avoid defects in the coating. Drying may be partly assisted by irradiation heat from infrared IR-lamps, in combination with hot air convection drying. For the coating of the ductile base layer pre-coating, however, the aqueous content is much lower and then also less drying will be needed.

[0252] A resulting web of a ductile base layer pre-coated paper substrate 34a may optionally be calendered by passing through at least one high pressure roller nip, and is then forwarded to cool off and further wound onto a reel for intermediate storage and later further subjected to gas barrier coating operations. The further coating operations may be vapour deposition coating of a barrier deposition coating 14, or a further dispersion coating operation of a gas barrier composition, as described above, to provide a barrier-coated cellulose-based substrate.

[0253] FIG. 3b shows a process 30b for the final lamination steps in the manufacturing of the packaging laminate 20a or 20b, of FIGS. 2a and 2b, respectively, after that the bulk layer 21a, 21b first has been laminated to the barrier-coated cellulose-based substrate 10a or 10b of FIG. 1a or FIG. 1b, (i.e. 25a or 25b of FIGS. 2a and 2b respectively).

[0254] As explained in connection to FIGS. 2a and 2b, the bulk layer paperboard 21a; 21b may be laminated to the barrier-coated paper substrate 10a; 10b; 25a; 25b by means of wet, cold dispersion adhesive lamination, or by means of melt extrusion lamination. The adhesive may be applied by means of a same or similar method as described in connection to FIG. 3a, however not requiring drying, or very little heating.

[0255] The resulting paper pre-laminate web 31b is forwarded from an intermediate storage reel, or directly from the lamination station for laminating the paper pre-laminate. The non-laminated side of the bulk layer 21a; 21b, i.e. its print side, is joined at a cooled roller nip 33 to a molten polymer curtain 32 of the LDPE, which is to form the outermost layer 22a; 22b of the laminated material, the LDPE being extruded from an extruder feedblock and die 32b. Subsequently, the paper pre-laminated web, now having the outermost layer 22a; 22b coated on its printed side, the outside, passes a second extruder feedblock and die 34b and a lamination nip 35, where a molten polymer curtain 34 is joined and coated onto the other side of the pre-laminate, i.e. on the barrier-coated side of the paper substrate 10; 25a; 25b. Thus, the innermost heat sealable layer(s) 23a are coextrusion coated onto the inner side of the paper pre-laminate web, to form the finished laminated packaging material 36, which is finally wound onto a storage reel, not shown.

[0256] These two coextrusion steps at lamination roller nips 33 and 35, may alternatively be performed as two consecutive steps in the opposite order.

[0257] According to another embodiment, one or both of the outermost layers may instead be applied in a pre-lamination station, where the coextrusion coated layer is first applied to the outside of the (printed) bulk paperboard layer or onto the metallisation coating of the barrier-coated paper substrate, and thereafter the two pre-laminated paper webs may be joined to each other, as described above.

[0258] According to a further embodiment, the innermost layers of the heat sealable and liquid-tight thermoplastic layers are applied in the form of a pre-manufactured film, which is laminated to the coated side of the barrier-coated paper substrate 10.

[0259] As explained in connection to FIGS. 2a and 2b, such an innermost layer 23a; 23b may be laminated to the barrier-coated paper substrate 10 by means of wet, cold dispersion adhesive lamination, or by means of melt extrusion lamination.

[0260] FIG. 4a is a diagrammatic view of an example of a plant 40a for physical vapour deposition, PVD, of e.g. an aluminium metal coating, onto a web substrate of the invention. The dispersion-coated paper substrate 41 is subjected, on its coated side, to continuous evaporation deposition 40, of evaporised aluminium, to form a metallised layer of aluminium or, alternatively to a mixture of oxygen with aluminium vapour, to form a deposited coating of aluminium oxide. The coating is provided at a thickness from 5 to 100 nm, preferably from 10 to 50 nm, to form the barrier-coated paper 43 of the invention. The aluminium vapour is formed from ion bombardment of an evaporation source of a solid piece of aluminium 42. For the coating of Aluminium oxide, also some oxygen gas may be injected into the plasma chamber via inlet ports.

[0261] FIG. 4b is a diagrammatic view of an example of a plant 40b for plasma enhanced chemical vapour deposition coating, PECVD, of e.g. hydrogenated amorphous diamond-like carbon coatings onto a web substrate of the invention. The web substrate 44a is subjected, on one of its surfaces, to continuous PECVD, of a plasma, in a plasma reaction zone 45 created in the space between magnetron electrodes 46, and a chilled web-transporting drum 47, which is also acting as an electrode, while the substrate is forwarded by the rotating drum, through the plasma reaction zone along the circumferential surface of the drum, and subsequently wound onto a roller as a barrier-coated web substrate 44b. The plasma for deposition coating of an amorphous DLC coating layer may for example be created from injecting a gas precursor composition comprising an organic hydrocarbon gas, such as acetylene or methane, into the plasma reaction chamber. Other gas barrier coatings may be applied by the same principal PECVD method, such as silicon oxide coatings, SiOx, then starting from a precursor gas of an organosilicon compound. The PECVD plasma chamber is kept at vacuum conditions by continuously evacuating the chamber at outlet ports 48a and 48b.

[0262] FIG. 5a shows an example of a packaging container 50a produced from a packaging laminate. The packaging container is particularly suitable for beverages, sauces, soups or the like. Typically, such a package has a volume of about 100 to 1000 ml. It may be of any configuration, but is preferably brick-shaped, having longitudinal and transversal seals 51a and 52a, respectively, and optionally an opening device 53. In another embodiment, not shown, the packaging container may be shaped as a wedge. In order to obtain such a wedge-shape, only the bottom part of the package is fold formed such that the transversal heat seal of the bottom is hidden under the triangular corner flaps, which are folded and sealed against the bottom of the package. The top section transversal seal is left unfolded. In this way the only partly folded packaging container is still easy to handle and dimensionally stable enough to put on a shelf in the food store or on any flat surface.

[0263] FIG. 5b shows an alternative example of a packaging container 50b produced from an alternative packaging laminate. The alternative packaging laminate is thinner by having a thinner paper bulk layer, and thus it is not dimensionally stable enough to form a parallel epidemic or wedge-shaped packaging container, and is not fold formed after transversal sealing 52b. The packaging container will remain a pillow-shaped pouch-like container and be distributed and sold in this form.

[0264] FIG. 5c shows a gable top package 50c, which is fold-formed from a pre-cut sheet or blank, from the laminated packaging material comprising a bulk layer of paperboard and the barrier-coated paper substrate of the invention. Also flat top packages may be formed from similar blanks of material.

[0265] FIG. 5d shows a bottle-like package 50d, which is a combination of a sleeve 54 formed from a pre-cut blank of the laminated packaging material, and a top 55, which is formed by injection moulding plastics in combination with an opening device such as a screw cork or the like. This type of packages are for example marketed under the trade names of Tetra Top and Tetra Evero. Those particular packages are formed by attaching the moulded top 55 with an opening device attached in a closed position, to a tubular sleeve 54 of the laminated packaging material, sterilizing the thus formed bottle-top capsule, filling it with the food product and finally fold-forming the bottom of the package and sealing it.

[0266] FIG. 6 shows the principle as described in the introduction of the present application, i.e. a web of packaging material is formed into a tube 61 by overlapping the longitudinal edges 62, 62 of the web and heat sealing them to one another, to thus form an overlap joint 63. The tube is continuously filled 64 with the liquid food product to be filled and is divided into individual, filled packages by repeated, double transversal seals 65 of the tube at a pre-determined distance from one another below the level of the filled contents in the tube. The packages 66 are separated by cutting between the double transversal seals (top seal and bottom seal) and are finally shaped into the desired geometric configuration by fold formation along prepared crease lines in the material.

[0267] FIG. 7 shows the effect of surface roughness on the oxygen transmission rate of the coated papers listed in Table 2, at 70% RH (ml/m.sup.2.Math.day).

[0268] FIG. 8 shows the principal structure of a the ductile cellulose-based substrate A, as pre-coated with a ductile base layer pre-coating B on its top side, and further, optionally coated with a similar ductile coating C on its backside.

[0269] As a final remark, the invention is not limited by the embodiments shown and described above, but may be varied within the scope of the claims.