BARRIER-COATED CELLULOSE-BASED SUBSTRATE, LAMINATED PACKAGING MATERIAL AND PACKAGING CONTAINER COMPRISING THE CELLULOSE-BASED SUBSTRATE

Abstract

The present invention relates to barrier-coated cellulose-based substrates and to a method of manufacturing such cellulose-based substrates, by dispersion coating of a barrier pre-coating and subsequent vapour deposition coating of a barrier deposition coating. The invention further relates to laminated packaging materials comprising the barrier-coated celluose-based substrates, in particular intended for liquid carton food packaging, and to liquid carton packaging containers comprising the laminated packaging material.

Claims

1. Barrier-coated cellulose-based substrate, for use as a barrier sheet in a laminated packaging material for liquid food products, comprising a cellulose-based substrate and applied on a first side of the cellulose-based substrate a barrier pre-coating, applied by dispersion or solution coating, and further onto the barrier pre-coating a barrier deposition coating, the barrier deposition coating being applied by a vapour deposition method, wherein the barrier-coated cellulose-based substrate further comprises a base layer pre-coating, which is different from the barrier pre-coating and applied by dispersion or solution coating onto the cellulose-based substrate and thus positioned directly adjacent and contacting the first side of the cellulose-based substrate layer, and positioned beneath the barrier pre-coating, the barrier-coated cellulose-based substrate thus being suitable for providing gas and water vapour barrier properties in a laminated packaging material and packages made thereof.

2. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the barrier pre-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.

3. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the barrier pre-coating has been applied by dispersion or solution coating at an amount of from 0.5 to 2 g/m.sup.2, dry weight.

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 a vapour deposition coating selected from the group consisting of an aluminium metallisation coating and aluminium oxide, AlOx, and preferably is an aluminium metallisation coating.

6. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the barrier deposition coating-44) is applied to a thickness of from 10 to 80 nm.

7. Barrier-coated cellulose-based substrate as claimed in claim 5, 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, measured as described herein.

8. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the base layer pre-coating comprises a polymer selected from the group consisting of starch, modified starch and cellulose ethers.

9. Barrier-coated cellulose-based substrate as claimed in claim 1, wherein the base layer pre-coating comprises a material selected from the group consisting of starch, modified starch, methyl cellulose, ethyl cellulose, carboxymethyl cellulose CMC, hydroxy ethyl cellulose HEC, hydroxy propyl cellulose HPC, hydroxypropylmethyl cellulose HPMC and sodium carboxymethyl cellulose NaCMC.

10. Barrier-coated cellulose-based substrate as claimed claim 1, wherein the base layer pre-coating has been applied by aqueous dispersion or solution coating at an amount of from 0.5 to 2 g/m.sup.2, dry weight.

11. Laminated packaging material comprising the barrier-coated cellulose-based substrate as claimed in claim 1, and further comprising a first outermost protective material layer and a second innermost liquid tight, heat sealable material layer.

12. Laminated packaging material as claimed in claim 11, wherein the second innermost liquid tight, heat sealable material layer comprises a polyolefin polymer.

13. Laminated packaging material according to claim 11, further comprising a bulk layer of paper or paperboard or other cellulose-based material, and, arranged on the inner side of the bulk layer of paper or paperboard, between the bulk layer and the second innermost liquid tight, heat sealable material layer, said barrier-coated cellulose-based substrate.

14. Laminated packaging material according to claim 13, wherein the barrier-coated cellulose-based substrate is bonded to the bulk layer by an intermediate bonding layer comprising a composition comprising a binder selected from the group consisting of acrylic polymers and copolymers, starch, cellulose and polysaccharide derivatives, polymers and copolymers of vinyl acetate and/or vinyl alcohol.

15. Laminated packaging material according to claim 12, wherein the second innermost liquid tight, heat sealable polyolefin layer is a pre-manufactured film comprising the same or similar polyolefins for improved robustness of the mechanical properties of the packaging material.

16. Packaging container comprising the laminated packaging material as defined in claim 11.

17. Method of manufacturing a barrier-coated cellulose-based substrate as claimed in claim 1, which comprises providing a cellulose-based substrate as a moving web in a roll to roll system, dispersion coating (liquid film coating) a first dispersion or solution of a base layer pre-coating composition, onto the moving cellulose-based substrate, and subsequently drying the applied base layer pre-coating by forced evaporation, dispersion coating a second dispersion or solution of a barrier pre-coating composition having different ingredients than the base layer pre-coating composition, onto the base-layer coated moving cellulose-based substrate, and subsequently drying the applied barrier pre-coating by forced evaporation, and further depositing onto the barrier pre-coating of the moving barrier pre-coated cellulose-based substrate, a barrier deposition coating by a vapour deposition coating operation.

18. Method as claimed in claim 17, wherein the base layer pre-coating composition is an aqueous dispersion of a material selected from the group consisting of starch, modified starch, methyl cellulose, ethyl cellulose, carboxymethyl cellulose CMC, hydroxy ethyl cellulose HEC, hydroxy propyl cellulose HPC, hydroxypropylmethyl cellulose HPMC and sodium carboxymethyl cellulose NaCMC.

Description

EXAMPLES AND DESCRIPTION OF PREFERRED EMBODIMENTS

[0095] In the following, preferred embodiments of the invention will be described with reference to the drawings, of which:

[0096] FIG. 1 schematically shows in cross-section an embodiment of a barrier-coated cellulose-based substrate according to the invention,

[0097] FIG. 2a shows a schematic, cross-sectional view of a laminated packaging material according to the invention, comprising the barrier-coated cellulose-based substrate of FIG. 1,

[0098] FIG. 2b is showing a schematic, cross-sectional view of a further laminated packaging material comprising the barrier-coated cellulose-based substrate of FIG. 1,

[0099] FIG. 3a shows schematically a method, for dispersion coating a base layer or barrier pre-coating composition onto a cellulose-based substrate,

[0100] FIG. 3b shows schematically a method, for melt (co-) extrusion coating layer(s) of a thermoplastic heat sealable and liquid-tigth polymer onto a web sustrate, to form innermost and outermost layers of a packaging laminate of the invention,

[0101] 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,

[0102] 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,

[0103] FIGS. 5a, 5b, 5c and 5d are showing typical examples of packaging containers produced from the laminated packaging material according to the invention, and

[0104] 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.

EXAMPLES

Example 1

[0105] Two different paper substrates of the type suitable for greaseproof wrapping were coated with base layer pre-coatings and/or barrier pre-coating layers at small pilot scale, according to what is shown in Table 1, without a further metallised aluminium barrier deposition coating onto the barrier pre-coating. Subsequently the coated paper substrates were laminated into packaging laminate structures as follows:

[0106] //outside 12 g/m.sup.2 LDPE/Duplex CLC 80 mN, 200 g/m.sup.2, paperboard bulk layer/3-4 g/m.sup.2 of aqueous PVAc adhesive/barrier pre-coated paper (as listed in Table 1)/6 g/m.sup.2 EAA adhesive polymer/22 g/m.sup.2 inside heat seal layer of a blend of LDPE and m-LLDPE//

[0107] 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. The paperboard bulk layer was laminated to the barrier-coated paper by wet lamination with an aqueous adhesive comprising polyvinyl acetate at low amount and without any intermediate drying step.

[0108] Oxygen transmission measurements were made with an Oxtran Mocon 2/21 equipment (an equipment based on coulometric sensors) at 23 C. and at 50% and 80% RH (relative humidity), respectively, and the measured values were reported in cc/m.sup.2, during 24 hours, at 1 atmosphere of 100% oxygen gas (air at 1 atm having only 20% oxygen gas).

[0109] Paper A was a greaseproof paper having a compact, dense surface, from Nordic Paper, identified as Super Perga WS Parchment having a grammage of 38 g/m.sup.2.

[0110] Paper B was a greaseproof paper from Arjo Wiggins, named Clearpack, having a grammage of 46 g/m.sup.2.

[0111] The papers were measured to have a surface roughness on the top side, i.e. the side to be barrier-coated, of about 200-300 ml/min Bendtsen and of about 150 ml/min Bendtsen, respectively.

[0112] The respective papers were thus coated only with base layer pre-coating and/or barrier pre-coating layers according to Table 1, i.e. with dispersion coated pre-coating layers, and then laminated into the same laminated packaging material structure. The pre-coating operations as well as the lamination operations to produce laminated packaging material structures from the pre-coated papers, were made in pilot scale and the oxygen transmission measurements were performed on the resulting packaging materials flat samples.

TABLE-US-00001 TABLE 1 Packaging Solvicol Poval OTR 23 C. /50% RH laminate Paper 1290 6-98 cc/m.sup.2, 24 h, 1 atm, sample substrate g/m.sup.2 g/m.sup.2 100% Oxygen 1 A 30 2 A 1 5.8 3 A 2 1 3.7 4 A 1 3.7 5 A 2 1 1.8 6 A 3 1 1.4 7 A 1 1 1.4 8 B 2.2 9 B 1 1.7 10 B 2 1 1.8 11 B 1 1.1 12 B 2 1 0.9 13 B 3 1 0.7 14 B 1 1 0.4

[0113] The barrier papers as listed in Table 1 were thus each laminated uncoated or dispersion-coated (the type of coating methods are generally known by the term liquid film coating, applicable for barrier pre-coating of aqueous dispersions or solutions of polymers at low amounts of dry weight onto a substrate) into the standardised laminated packaging material structure above. The base layer pre-coatings and barrier pre-coatings were applied in 1-3 steps as listed, at a dry coating weight of about 1 g/m.sup.2 each, with intermediate drying steps in between each coating. Two types of aqueous dispersions and/or solutions were used, i.e. a water-based dispersion of native potato-based starch of the brand Solvicol from Avebe, and a solution of polyvinyl alcohol, PVOH, from Kuraray having a degree of hydrolysis of at least 98%, i.e. Poval 6-98. When a starch pre-coating is applied in combination with a PVOH pre-coating for the purpose of forming a barrier-coated paper, the starch coating is applied as a first, base layer pre-coating, which is dried in an in-line dryer equipment and subsequently over-coated with a further, barrier pre-coating of PVOH, further and subsequently dried in an in-line dryer in a second drying step. The dispersions were applied by means of a gravure-coating method in pilot-scale equipment, and the dry content of the aqueous dispersion of the PVOH was about 15 weight-%. The temperature of the substrate surface at each drying operation was regulated to from about 60 to about 80 C.

[0114] The dry content and viscosity of the starch dispersion was selected such that the low amount of dry content of the starch may be applied by a gravure coating process, at industrial speed. The base layer pre-coating was applied as a rich, well-adhering, dense and homogenous base pre-coating to enable the subsequent application of an even, low amount of the barrier dispersion pre-coating. The resulting even and smooth surface of the thus dried barrier pre-coating in turn enables the application of a further high-quality vapour deposition coating, being coherent, homogenous without pinholes, and adhering well to the dried barrier pre-coating surface.

[0115] Accordingly, the coatings were applied in 2-3 consecutive coating steps, to a dry matter weight of about 1 g/m.sup.2 in each coating step, with drying of each applied coating between the coating steps.

[0116] It can be concluded from the sample laminated materials comprising the paper substrate pre-coated with base layer and/or pre-coated with barrier coatings in accordance with Table 1, that one or two coatings of starch only improve the oxygen barrier properties to some extent of each of the pre-coated papers in a laminated material, but that the improvement is greater in the case of Paper A, which had a greater initial surface roughness and which exhibited a lower inherent oxygen barrier properties when laminated into the multilayer laminate structure. The pre-coated papers having two or three coatings of the PVOH coating only, have further improved barrier properties than papers having coatings with starch only, partly because starch inherently contributes less by its inherent gas barrier material properties. A significant further improvement was seen, however, when combining the two types of pre-coatings in the order as defined by samples 7 and 14. i.e. a first base layer pre-coating of starch and a second barrier pre-coating of PVOH. Such a further, unexpected improvement of the resulting oxygen barrier of the final laminate was even more notable when Paper B was used, i.e. the paper having greater smoothness and higher inherent barrier properties. Then the OTR of Sample 14 was even further reduced by 50%, compared to samples 12-13, wherein only the higher barrier pre-coating PVOH layers were applied.

Example 2

[0117] Further, similar barrier coating experiments were performed on the two types of papers A and B, in more full-scale production, as listed in samples 7 and 14 in Table 1, and the thus barrier pre-coated papers with a first base layer pre-coating and second barrier pre-coating were metallised and subsequently laminated in the same way into laminated multilayer packaging material structures. The speed of the dispersion coating operations were from 400 to 600 m/min, and the coatings were applied in 2 consecutive coating steps, to a dry matter weight of about 1 g/m.sup.2 each, with drying of each applied coating between the coating steps. As in Example 1, the drying was carried out at a substrate surface temperature of from about 60 to about 80 C. In a subsequent, separate coating operation, metallisation barrier coatings were applied onto the barrier pre-coating by physical vapour deposition to an optical density of about 2,0, as measured by a light transmission densitometer, and a thickness of about 40 nm.

[0118] Packaging laminate samples were also prepared from the pre-coated paper substrates, not having the metallisation coating of aluminium applied.

[0119] The results from this experiment are listed in Table 2.

TABLE-US-00002 TABLE 2 Base OTR OTR layer Barrier Pre- 23 C./50% 23 C./80% pre- pre- coating Metal- RH, cc/m.sup.2, RH, cc/m.sup.2, coating coating application lisation 24 h, 24 h, Solvicol Poval line barrier 1 atm, 1 atm, WVTR 1290 6-98 speed coating 100% 100% 38/90 No. Paper g/m.sup.2 g/m.sup.2 m/min (nm) Oxygen Oxygen g/m.sup.2 2.1 B 1 1 400 40 3.6 4.7 2.5 2.2 B 1 1 600 40 2.0 4.2 3.3 2.3 A 1 1 400 40 2.5 4.7 5.7 2.4 B 1 1 600 0 4.4 18.3 11.5 2.5 A 1 1 400 0 4.6 24.1 11.9 2.6 A 1 1 600 0 3.4 30.2 12.0

[0120] From the full-scale experiments, we see a further improved oxygen barrier (lower oxygen transmission) in the sample corresponding to sample 7 of Table 1, i.e. from barrier pre-coatings onto Paper A, and to sample 14, i.e. from barrier pre-coatings onto Paper B, by the over-coating of further metallisation coating. See sample 2.3 vs samples 2.5 and 2.6 for Paper A, and samples 2.1 and 2.2 vs sample 2.4, regarding Paper B.

[0121] It was not perceived that the coating speed mattered significantly to the resulting OTR measurements, since the amount of the applied dry weight of the coatings was adjusted to approximately 1 g/m.sup.2 at each different speed. The different coating operations at industrial speeds such as 400-600 m/min was thus not perceived to pose any problems to the coating quality or efficiency.

[0122] As can be seen from the OTR measurements at 80% relative humidity for the laminate samples including also the metallisation coating, the effect of the different contributions from the different paper grades and the possible variations in the metallisation coatings are levelled out and the oxygen barrier results seem to land at the same high level (i.e. the same low OTR values), thanks to the synergy between the combination of the base layer pre-coating and the barrier pre-coating and the metallisation barrier coating. Some differences in the water vapour transmission values were noted and believed due to differences between the quality and thicknesses of the metallised barrier coatings in the different laminate configurations. By comparing the OTR values of the laminate samples with and without the metallization barrier coating onto the barrier pre-coated paper substrate at 80% relative humidity, which is the more realistic environment for a filled, liquid food carton packaging container, there is thus a 4-5 times improvement of the oxygen barrier of the laminated packaging materials having the specific combination of a base layer pre-coating, a barrier pre-coating and a barrier deposition coating.

[0123] Laminated packaging materials such as those produced with the configuration of sample 2.3 in Table 2 were further evaluated in limited filling machine trials for forming and filling and sealing into filled packaging. No major problems regarding packaging integrity (i.e. package tightness vs the surrounding environment) and sealability properties were identified during the trials, which therefore were considered successful.

[0124] Further, similar barrier paper laminate structures were evaluated in the same trials, with the only difference to the laminate configuration that they had a pre-manufactured blown film of polyethylene on the inside, comprising at least one part-layer with a major proportion of linear low density polyethylene (LLDPE), and thus constituting the innermost heat sealable layer portion applied on the inside of the barrier-coated paper. From the results and perceptions in evaluating the trials, it was concluded that laminate configurations having such a pre-manufactured heat sealable film on the inside would be favourable for further increased robustness of the laminated packaging material.

[0125] Further, relating to the attached figures:

[0126] In FIG. 1, there is shown, in cross-section, an embodiment of a barrier-coated paper substrate 10, of the invention. The paper substrate 11 is a paper of the type greaseproof paper Nordic Paper Super Perga WS Plus having a grammage of 38 g/m.sup.2, provided with a first base layer pre-coating 12 of starch, Solvicol from Avebe, which has been applied by means of aqueous dispersion coating and subsequently heat dried to evaporate off the water. The dry weight of the starch base layer pre-coating is about 1 g/m.sup.2. Further, the paper substrate has a second barrier pre-coating 13 of PVOH, Poval 6-98 from Kuraray, applied on the surface of the first base layer coating. The barrier pre-coating layer 13 has also been applied by means of aqueous dispersion coating and subsequently heat dried to evaporate off the water. The dry weight of the PVOH barrier pre-coating is about 1 g/m.sup.2. Further, the pre-coated barrier paper substrate has an aluminium barrier deposition coating 14, i.e. an aluminium-metallised layer, applied onto the dried surface of the barrier pre-coating 13, by physical vapour deposition, to an OD of about 2, and a thickness of about 40 nm.

[0127] 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 polyolefin 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 dcor 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 polyolefin 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). It is applied at an amount of about 22 g/m.sup.2.

[0128] The bulk layer 21a is laminated to the uncoated side of the barrier-coated paper substrate 10, from FIG. 1, i.e. 25a, 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 thickness of the intermediate bonding layer 26a is from 12 to 18 m, such as from 12-15 m.

[0129] 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 14 of the barrier paper substrate 10, by an intermediate coextruded tie layer, e.g. of ethylene acrylic acid copolymer (EAA) which thus bonds the innermost heat sealable layer(s) to the barrier coated paper substrate 10, in applying the layers together in a single melt coextrusion coating step.

[0130] In FIG. 2b, a different laminated packaging material 20b of the invention, 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 polyolefin applied on the outside of the bulk layer 21b, which side is to be directed towards the outside of a packaging container produced from the packaging laminate. The polyolefin of the outer layer 22b is a conventional low density polyethylene (LDPE) of a heat sealable quality and has been applied at an amount of 12 g/m.sup.2, but may include further similar polymers, including LLDPEs. An innermost liquid tight and heat sealable layer 23b is arranged on the opposite side of the bulk layer 21b, which is to be directed towards the inside of a packaging container produced from the packaging laminate, i.e. the layer 23b will be in direct contact with the packaged product. The thus innermost heat sealable layer 23b, which is to form strong 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).

[0131] The bulk layer 21b is laminated to the barrier-coated paper substrate described in FIG. 1, 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 onto one of the surfaces to be adhered to each other and subsequently pressing together in a roller nip. This 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 amount applied of the intermediate bonding layer 26b is from 3 to 4 g/m.sup.2 only, which explains that there is no need for drying and evaporation.

[0132] 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 polyethylene, described in FIG. 2a.

[0133] Alternatively, the innermost heat sealable and liquid-tight layer 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 24b, comprising a thicker tie layer of EAA than used in FIG. 2a, or a more simple bonding layer of LDPE, which is from 12 to 20 m, such as from 12 to 18 m, thick.

[0134] In an alternative embodiment, the pre-manufactured blown film 23b is laminated to the metallised coating by means of another wet lamination step, with an aqueous adhesive of an acrylic (co)polymer adhesive layer 24b, at ambient (cold) temperature, at an amount from 3 to 4 g/m.sup.2.

[0135] A further embodiment, having all the features as described and a melt extruded bulk layer lamination layer 26a of FIG. 2a, but which is instead combined with the feature of an innermost heat sealable layer configuration 23b, applied either by means of melt extrusion lamination with a layer 24b, or by means of wet laminating a pre-manufactured film, 24b, as described in connection to FIG. 2b, is also hereby disclosed.

[0136] A yet further embodiment, wherein the thin, wet, aqueous adhesive dispersion laminated layer 26a of FIG. 2b is combined with the conventional melt coextrusion coated inside layers 24a and 23a, is hereby also disclosed.

[0137] In FIG. 3a, a process of aqueous dispersion coating 30a is shown, which may be used for applying the base layer pre-coating 12 and the barrier pre-coating 13. The paper substrate web 31a (e.g. the paper 11 from FIG. 1) 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. If the surfaces of the two sides of the substrate are different, usually there is one side more suitable for receiving a coating or a printed dcor pattern, and this is thus the surface to be coated for this invention (often that side is called the top side or the print side). Since the dispersion composition has an aqueous content of from 80 to 99 weight-%, there will 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, is kept constant at a temperature of from 60 to 80 C. Alternatively, dyring may be partly assisted by irradiation heat from infrared IR-lamps, in combination with hot air convection drying.

[0138] The resulting barrier pre-coated paper substrate web 34a is forwarded to cool off and is wounded onto a reel for intermediate storage and later further vapour deposition coating of a barrier deposition coating 14, onto the barrier pre-coated paper.

[0139] FIG. 3b shows a process for the final lamination steps in the manufacturing of the packaging laminate 20a or 20b, of FIGS. 2a and 2b, respectively, after the bulk layer 21a, 21b has been first laminated to the barrier-coated paper substrate 10 of FIG. 1, (i.e. 25a or 25b of FIGS. 2a and 2b respectively).

[0140] As explained in connection to FIGS. 2a and 2b, the bulk layer paperboard 21a,21b may be laminated to the barrier-coated paper substrate 10; 25a; 25b by means of wet, cold dispersion adhesive lamination, or by means of melt extrusion lamination.

[0141] 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.

[0142] These two coextrusion steps at lamination roller nips 33 and 35, may alternatively be performed as two consecutive steps in the opposite order.

[0143] 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.

[0144] 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.

[0145] As explained in connection to FIGS. 2a and 2b, such an innermost layer 23a; 23 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.

[0146] FIG. 4a is a diagrammatic view of an example of a plant for physical vapour deposition, PVD, of e.g. an aluminium metal coating, onto a web substrate of the invention. The pre-coated paper substrate 44a is subjected, on its pre-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, so that the barrier-coated paper 43 of the invention is formed. The aluminium vapour is formed from ion bombardment of an evaporation source of a solid piece of aluminium 41. For the coating of Aluminium oxide, also some oxygen gas may be injected into the plasma chamber via inlet ports.

[0147] FIG. 4b is a diagrammatic view of an example of a plant 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 44b is subjected, on one of its surfaces, to continuous PECVD, of a plasma 50, in a plasma reaction zone created in the space between magnetron electrodes 45, and a chilled web-transporting drum 46, which is also acting as an electrode, while the film is forwarded by the rotating drum, through the plasma reaction zone along the circumferential surface of the drum. 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.

[0148] FIG. 5a shows an embodiment of a packaging container 50a produced from a packaging laminate according to the invention. 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 is easy to handle and dimensionally stable enough to put on a shelf in the food store or on any flat surface.

[0149] FIG. 5b shows an alternative example of a packaging container 50b produced from an alternative packaging laminate according to the invention. The alternative packaging laminate is thinner by having a thinner paper bulk layer, and thus it is not dimensionally stable enough to form a parallellepipedic 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.

[0150] 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.

[0151] FIG. 5d shows a bottle-like package 50d, which is a combination of a sleeve 54 formed from a pre-cut blanks of the laminated packaging material of the invention, 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.

[0152] 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.

[0153] 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.