EP4649197A1

EP4649197A1 - Oxygen barrier material

Info

Publication number: EP4649197A1
Application number: EP24700333.8A
Authority: EP
Inventors: Esa SAUKKONEN; Christiane Laine; Kirsi LAHTELA; Mika UUSIKARTANO
Original assignee: UPM Kymmene Oy
Current assignee: UPM Kymmene Oy
Priority date: 2023-01-10
Filing date: 2024-01-10
Publication date: 2025-11-19
Also published as: WO2024149938A1; CN120604008A

Abstract

The invention relates to a method for manufacturing an oxygen barrier material comprising: supplying a support layer, the support layer comprising a paper and a first coating layer, applying a second coating on the support layer by an extrusion technique, thereby forming a second coating layer on the support layer, a grammage of the second coating being in a range between 5 and 50 g/m², wherein the second coating layer is compostable and/or biodegradable in industrial composting so that it is at least 90% biodegradable in 6 months, polymeric materials in the first coatings are biodegradable, and the oxygen barrier material is compostable, wherein the oxygen barrier material has an oxygen barrier value of less than 70 cc/m^2*day. The invention further relates to an oxygen barrier material.

Description

Oxygen barrier material

Technical field

The specification relates to a method for manufacturing an oxygen barrier material. The specification also relates to an oxygen barrier material.

Background

A large variety of barrier materials is manufactured in industry. For example, for packaging materials, properties and the desired shelf life of the products to be packaged typically determine the packaging material used for packaging each product.

Materials used for obtaining desired barrier properties can be selected so that if e.g., good water barrier properties as well as good oxygen barrier properties are needed, a barrier laminate material can comprise one material layer having excellent water barrier properties and one material layer having excellent oxygen barrier properties. In industry, however, there is still need for new barrier materials.

Summary

It is an aim of this specification to present an oxygen barrier material. Furthermore, it is an aim of this specification to present a method for manufacturing an oxygen barrier material.

Aspects of the invention are characterized by what is stated in the independent claims. Preferred embodiments are disclosed in the dependent claims. These and other embodiments are disclosed in the description and figures.

This specification provides a solution for obtaining a fiber-based oxygen barrier material by extrusion coating.

A method for manufacturing an oxygen barrier material can comprise the following steps: supplying a support layer having a density of equal to or less than 1000 kg/m³, preferably between 800 kg/m³ and 990 kg/m³, more preferably less than 940 kg/m³, the support layer comprising a paper comprising cellulose-containing natural fibres, and a first coating layer on at least one surface of the paper, the first coating layer containing a binding agent, wherein a grammage of the first coating layer is in a range between 2 and 10 gsm, applying a second coating on one or both sides of the support layer by an extrusion technique, thereby forming a second coating layer on one or both sides of the support layer, a grammage of the second coating layer being in a range between 5 and 50 gsm, wherein

A) - the second coating layer is compostable and/or biodegradable in industrial composting so that it is at least 90% biodegradable in 6 months, determined according to standard EN 13432, and

- polymeric materials in the first coatings are biodegradable according to standard OECD 301 , and

- the oxygen barrier material is compostable according to standard EN 13432, and

B) the oxygen barrier material has an oxygen barrier value of less than 70 cc/m²*day, preferably less than 50 cc/m²*day, and more preferably less than 20 cc/m²*day, measured according to ISO 15105-2 at 23°C/50%RH.

An oxygen barrier material can comprise a support layer having a density of equal to or less than 1000 kg/m³, preferably between 800 kg/m³ and 990 kg/m³, more preferably less than 940 kg/m³, the support layer comprising a paper comprising cellulose-containing natural fibres, and a first coating layer containing a binding agent on at least one surface of the paper, a grammage of the first coating layer being in a range between 2 and 10 gsm, and a second coating layer on at least one side of the support layer, a grammage of the second coating layer being in a range between 5 and 50 gsm, wherein

The second coating layer is preferably on the same side as the first coating layer, on the first coating layer. Technical effect is to obtain improved oxygen barrier properties. Preferably, the second coating layer is directly on the first coating layer. However, there may be a tie layer between the first coating layer and the second coating layer to improve adhesion of the first and the second coating layers. The adhesion, with or without the tie layer, is preferably adjusted so that the adhesion between the support layer and the second coating layer is sufficient for processing in converting but enabling (even manual) separation of the support layer and the second coating.

Thus, the second coating layer and the first coating layer are preferably on a first side of the paper. The oxygen barrier material can further comprise a third coating layer on a second side of the paper. The third coating layer can comprise or consist of starch The third coating layer preferably comprises starch equal to or more than 80 wt.%, determined from total dry weight of the third coating layer. A grammage of the third coating layer is preferably 0.5-1 .5 gsm, preferably 0.7-1 .3 gsm, more preferably 0.8-1 .2 gsm.

The support layer can have an oxygen barrier of equal to or more than 500 cc/m²*day, preferably equal to or more than 1000 cc/m²*day, most preferably over 5000 cc/m²*day. Alternative or in addition, the second coating layer can have an oxygen barrier of more than 90 cc/m²*day, preferably equal to or more than 100 cc/m²*day, most preferably over 150 cc/m²*day. Technical effect is to provide improved barrier properties for the oxygen barrier material cost- efficiently. Another technical effect is to provide environmentally friendly material as materials without high oxygen barrier can be used for the layers.

The first coating layer can contain a binding agent selected from: starch, modified starch, enzymatically converted starch, polyvinyl alcohol, modified cellulose, biodegradable polyester, and their mixtures. The binding agent is preferably selected from: polyvinyl alcohol, starch, modified starch, enzymatically converted starch, modified cellulose, and their mixtures. Technical effects of these materials include improved environmental friendliness.

In an advantageous embodiment, the second coating layer comprises at least one of: polybutylene succinate, polyhydroxyalkanoate, polylactic acid, co- or terpolymers of glycolide and/or lactide, and polybutylene adipate terephthalate. Preferably, the second coating layer comprises polybutylene succinate. Technical effects of these materials include improved environmental friendliness, as these materials are at least industrially compostable and thus enable industrial compostability of the whole structure of the oxygen barrier material. The second coating layer can have a mineral oil barrier (Heptane vapour transmission rate) of less than 10 g/m²*day. Alternatively, or in addition, the support layer can have a mineral oil barrier (Heptane vapour transmission rate) of at least 100 g/m²*day. Further, the oxygen barrier material can have a mineral oil barrier (Heptane vapour transmission rate) of less than 2 g/m²*day. Technical effect is to improve, cost efficiently, mineral oil barrier properties for the obtained oxygen barrier material. Another technical effect is to provide environmentally friendly material as biobased materials without high mineral oil barrier can be used for the layers.

WVTR value of the support layer can be higher than 500 g/m²*day. Alternatively, or in addition, WVTR value of the second coating layer can be higher than 100 g/m²*day. The oxygen barrier material can have a WVTR value of less than 100 g/m²*day. WVTR value is determined at 23°C/85%RH according to standard ISO 2528. A technical effect is to provide environmentally friendly material having a good WVTR value with biobased materials.

The support layer can have a grease barrier less than 2 hours. Alternatively, or in addition, the second coating layer has a grease barrier less than 36 hours. The oxygen barrier material can have a grease barrier over 72 hours. The grease barrier is determined according to ASTM F119-82 at 40°C by using chicken fat. Technical effect is to improve, cost efficiently, grease barrier properties for the obtained oxygen barrier material. Another technical effect is to provide environmentally friendly material as biobased materials without high grease barrier can be used for the layers.

A transparency of the support layer can be below 65%, preferably below 50%, determined according to standard DIN 53146. Technical effect is to save energy in the paper production due to better dewatering properties.

A Gurley Hill air permeability of the support layer can be more than 100 s/100 ml, preferably in a range between 100 s/100 ml and 3000 s/100 ml.

The second coating layer can have a tailored adhesion with the support layer, which tailored adhesion can be selected so that it enables manual separation of the second coating layer from the support layer at 23°C and relative humidity of 50% without fibers stuck to the second coating layer.

Surprisingly, a material with good oxygen barrier properties was obtained even when a substrate having no or low oxygen barrier was extrusion coated with a polymer having no or low oxygen barrier. In this application the term “low oxygen barrier” refers to an oxygen barrier rate of more than 80 cc/m²*day, such as more than 100 cc/m²*day, and typically more than 200 cc/m²*day.

The coating layers of the oxygen barrier material can be nanocellulose free. Technical effect is to obtain a nanocellulose free route to obtain desired oxygen barrier values. Another technical effect is to decrease energy consumption of the manufacturing process.

The coating layers of the oxygen barrier material can be polyethylene free, more preferably polyolefin free. Technical effect is to obtain environmentally friendly, polyethylene free route to obtain desired oxygen barrier values.

The oxygen barrier material according to this specification can be a packaging material.

The solution according to this specification can provide flexible or rigid packaging applications for food, beverages as well as for non-food, where oxygen barrier values are needed. Preferably, the resulting oxygen barrier material is tailorable to enhance recyclability.

The oxygen barrier material comprises the first coating layer and the second coating layer, which both can be composed of biodegradable materials.

The oxygen barrier material according to the specification can be manufactured in an environmentally friendly way so that the oxygen barrier material can be, for example, recycled and/or composted after usage. As known by a person skilled in the art, plastic pollution is a significant environmental burden. By using the first and the second coating layers according to this specification instead of other packaging polymers, many environmental related problems can be solved.

Thus, thanks to the novel oxygen barrier material, predetermined oxygen barrier properties can be obtained in an environmentally friendly way. Conventionally, plastic multilayer laminates and paper-plastic laminates having oxygen barrier properties have a such multilayer structure which complicate the recyclability of the material. Thanks to the novel material, higher fiber recovery yield can be enabled in recycling processes.

Further, thanks to the novel oxygen barrier material, the second coating layer can have a tailored adhesion with the support layer, which is sufficient for processing in converting but enabling (even manual) separation of the support layer and the second coating. Advantageously, the second coating layer is heat sealable at least at 120°C. More preferably, heat sealability can be reached in any temperature in a range from 100 to 200 °C.

The coating layers in the oxygen barrier material can be at least 90%, preferably completely (100%), biodegradable and compostable within 6 months. For example, at least 90% of the oxygen barrier material is disintegrated under aerobic conditions in industrial composting to carbon dioxide, water, and biomass in such a way that the disintegration products have no ecotoxic effects. The biodegradability and compostability of the oxygen barrier can be determined according to the standard EN 13432.

Chemically unmodified constituents of natural origin, such as wood, wood fibre, starch, and paper mass, can be considered biodegradable materials without testing.

With certain material selection, the oxygen barrier material can also be home compostable so that it is at least 90% biodegradable in 6 months in a compost at 20-30°C, determined according to the standard EN 13432. Other material selections may be biodegradable even in water (EN ISO 14851 , EN ISO 14852, EN ISO 17556, EN ISO 19679/18830 or EN ISO 22404) and/or comply with Ready Biodegradability guidelines conditions (according to OECD (1992), Test No. 301 : Ready Biodegradability, OECD Guidelines for the Testing of Chemicals, Section 3, OECD Publishing, Paris). This applies e.g. for binders such as starch, modified starch, enzymatically converted starch and polyvinyl alcohol, or their combinations, in the first coating layer and e.g. polyhydroxyalkanoates such as PHB, PHBV, PHBH, P3HB4HB, PCL, or certain copolymers of lactic acid in the second coating layer.

Biodegradability refers to the disintegration of an organic chemical compound by means of microorganisms in the presence of oxygen to carbon dioxide, water, and mineral salts of the elements present, as well as biomass. Requirements for the complete compostability of a material are complete biodegradability and the fact that the disintegration products have no unfavorable effect on the quality of the compost. For example, the disintegration products have no ecotoxic effects.

The germinability of a plant species grown in a compost that contains disintegrated oxygen barrier material is advantageously higher than 90% compared with a compost with no disintegration products of said material. Brief of the

In the following, the invention will be described in more detail with reference to the appended drawings, in which:

Figs 1 a-d show examples of oxygen barrier materials in cross-section,

Figs 2a-2b and Figs 3a-3b show examples of laminated structures comprising a support layer and a second coating layer,

Figs 4 shows a reduced schematic chart of an example for manufacturing an oxygen barrier material,

Fig. 5a discloses microscopic pictures of the second coating layer after removal from the support layer with first coating, wherein the shape of fibers and pigments pressed against the film are visible but the detached second coating layer is in practice free from fibers and pigments, and

Fig. 5b discloses microscopic pictures of the second coating layer after removal from the support layer without first coating, wherein quite many fibers and pigments remain on the surface of the second coating layer after the removal from the support layer.

The Figures are intended to illustrate the general principles of the disclosed solution. Therefore, the illustrations in the Figures are not necessarily in scale or suggestive of precise layout of system components.

Detailed

In the text, references are made to the figures with the following numerals and denotations:

1 support layer including a base paper and a first coating layer,

2 paper, i.e., base paper, uncoated paper,

3 first coating layer,

4 second coating layer,

5 third coating layer,

6 tie layer,

7 first coating,

8 second coating,

9 extruder,

10 oxygen barrier material, and

11 first coating unit.

Terms and standards Unless otherwise indicated, the following standards refer to methods which are used in obtaining stated values of parameters representing quality of the packaging material:

1 ) Grammage ISO 536:2019

2) Density ISO 534:2011

3) WVTR ISO 2528 at 23°C/85%RH

4) Oxygen barrier ISO 15105-2 at 23°C/50%RH

5) Grease barrier ASTM F1 19-82 at 40°C by using chicken fat

6) Compostability and biodegradability EN 13432, or OECD 301

7) Transparency DIN 53146

8) Gurley Hill air permeability ISO 5636-5:2003

9) Roughness ISO 2494

10)Mineral oil barrier: Heptane vapor transmission rate (HVTR) is determined by a gravimetric method adapted from the method described in Gaudreault et al. 2013 (R. Gaudreault, C. Brochu, R. Sandrosck, P. Deglmann, H. Seyffer and A. Tetreault. Overview of practical and theoretical aspects of mineral oil contaminants in mill process and paperboards. In Advances in Pulp and Paper Research, Cambridge 2013, Trans, of the XVth Fund. Res. Symp. Cambridge, 2013, (S.J. I’Anson, ed.), pp 907-925, FRC, Manchester, 2018. DOI: 10.15376/frc.2013.2.907. A sponge soaked in n-heptane is placed in a test cup, that is then covered with the tested paper, barrier side down. Cup edges are then sealed with molten wax, and the filled and sealed cups are kept at standard conditions (50 % relative humidity and 23°C). The cups are weighed immediately after sealing, and then after 2h, 3h, 5h, and 25h. The HVTR is determined according to the equation in Gaudreault et al. 2013.

11 )Adhesion to the paper substrate is determined on a scale from 0 to 5, the highest figure representing the best adhesion. The polymeric coatings are introduced onto the substrate by extrusion, and their adhesion to the paper surface is defined on said scale, whereby the classification is as follows:

1 = no adhesion, the polymeric layer peels off;

2 = poor adhesion, some fibres are stuck to the polymeric layer that peels off;

3 = poor adhesion, when detaching the polymeric layer, less than 50 % of the paper breaks in the area of coating;

4 = moderate adhesion, when detaching the polymeric layer, over 50 % of the paper board breaks in the area of coating; 5 = perfect adhesion, when detaching the polymeric layer, the paper board breaks throughout the area of coating.

12)Recycling tests according to PTS METHOD PTS-RH 021/97, October 2012, replaces version September 1997: ‘Testing of raw materials, pulps and additives of paper manufacture - Identification of the recyclability of paper and board packages and of graphic print products’

For the purpose of the present description and the claims, unless otherwise indicated, all ranges include any combination of the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

The embodiments and examples recited in the claims and in the description are mutually freely combinable unless otherwise explicitly stated.

In this specification, the term “comprising” may be used as an open term, but it also comprises the closed term “consisting of’. Thus, unless otherwise indicated, the word “comprising” can be read as “comprising or consisting of’.

Percentage values relating to an amount of a material are percentages by weight (wt.%) unless otherwise indicated. All percentage values relating to an amount of a material refer to dry weight, unless otherwise indicated.

The term ‘WVTR’ refers to water vapour transmission rate. Unless otherwise indicated, the term WVTR refers to water vapour barrier at conditions of RH 85%, temperature 23°C.

In this application, all the contents (percentages) are in dry weight, unless otherwise expressed.

The term ‘gsm’ refers to grams per square meter (g/m²). Unless otherwise expressed, all the grammages are in dry weight.

The term ‘RH’ relates to relative humidity of the air.

The terms “paper” and “base paper” refers to an uncoated paper.

The term “support layer” refers to a coated paper comprising a first coating layer on a base paper.

Support layer The support layer 1 comprises a base paper 2 and a first coating layer 3.

The support layer and the base paper therein has a first side and a second side. Preferably, the first coating layer 3 is on the first side of the base paper 2.

The base paper 2 comprises cellulose-containing natural fibers, typically as its main raw material, and can further comprise, for example, one or more fillers and/or additives.

The term ‘cellulose-containing natural fiber’ refers to any plant material that contains cellulose. The natural fiber can be of wood origin, and/or it may comprise other than wood-based natural fibers. Other than wood-based raw materials may include agricultural waste, grasses and/or other plant materials, such as straw, leaves, bark, seeds, legumes, flowers, tops, or fruit, which may have been obtained from cotton, corn, wheat, oat, rye, barley, rice, flax, hemp, manila hemp, sisal hemp, jute, ramee, kenaf hemp, bagasse, bamboo, and/or reed.

Preferably, the base paper 2 comprises cellulose-containing natural fibers which are of wood origin. The base paper 2 can comprise fibers from softwood trees, such as spruce, pine, fir, larch, douglas-fir, or hemlock, or from hardwood trees, such as birch, aspen, poplar, alder, eucalyptus, or acacia, or from a mixture of softwoods and hardwoods.

Preferably, the cellulose-containing natural fibers comprises chemically pulped natural fibre, that is, pulp made in a chemical pulping process. In an advantageous example, the content of chemically pulped natural fibres in all the cellulose-containing natural fibers used in the base paper product is thus at least 70 wt.%, at least 80 wt.% or at least 90 wt.%, advantageously at least 95 wt.% or 98 wt.%. Preferably, all the cellulose-containing natural fibers used in the base paper are chemically pulped cellulose-containing natural fibers. Preferably, the base paper does not contain so-called mechanical pulp.

The base paper refers to an uncoated structure. As discussed, the support layer 1 has, in addition to the base paper 2, the first coating layer 3. Thus, the base paper can be coated with a first coating 7 to obtain the support layer 1 .

The support layer can have the first coating layer 3 on one or both sides of the base paper 2. Preferably, the support layer has the first coating layer 3 only on the first side of the paper. The second side of the paper can have a third coating layer 5. Thus, preferably, the first coating layer 3 is on the first side of the base paper 2, and the third coating layer 5, preferably essentially consisting of a starch, is on the second side of the base paper 2.

The first coating layer 3 can comprise a single coating layer, or it can be a multilayer structure comprising several layers, such as two, or three layers. Thus, in an embodiment, the first coating layer is made of two or three layers. Technical effect is to further enhance barrier properties, particularly water vapor barrier properties.

Preferably, the first coating layer comprises only one layer on one side of the support layer or, alternatively, only one layer on both sides of the support layer. The technical effect is to simplify the process and reduce manufacturing costs of the material.

In an advantageous embodiment, wherein the paper has the first coating layer only on one side, the paper preferably has the third coating layer on the other side of the paper. The third coating layer 5 preferably comprises starch, more preferably at least essentially consists of starch.

In an embodiment, the oxygen barrier material has the third coating layer and, furthermore, an additional coating layer on the third coating layer for improving printability of the oxygen barrier material. The additional coating layer may comprise e.g. a binder 8-15% (by dry weight), preferably 10-13% (by dry weight), and pigments up to 89% (by dry weight). In this embodiment, grammage of said additional coating layer can be, for example, 8-13 gsm.

The first coating layer can have a grammage in a range between 2 gsm and 10 gsm, preferably at least 3 gsm and less than 6 gsm. Technical effect is to provide improved surface in order to achieve full surface coverage with lower coat weight of the second coating.

Preferably, the grammage of the first coating is 3 to 10 gsm, more preferably 3.5 to 9 gsm, and most preferably from 4 to 8.5 gsm. Technical effect is to prepare the surface of the support layer 1 for further coating and to work as an adhesion promoter to another coating layer. Another technical effect is that first coating layer 3 and the second coating layer create a synergistic effect providing an oxygen barrier property for the oxygen barrier material 10.

Thickness of the first coating layer is preferably between 2 to 10 pm, and more preferably between 3.5 pm and 9 pm, and most preferably from 4 to 8.5 pm. Technical effect is to obtain protection from oxygen cost efficiently with the second coating. The first coating contains a binding agent.

The first coating can have a binding agent content of at least 25 wt.% (by dry weight), preferably at least 32%, such as in a range between 35% and 60% (by dry weight), and most preferably in a range between 35% and 50% (by dry weight), referring to relative proportion of the binding agent(s) in the total content of the first coating.

The binding agent can be selected from: dispersions of different polyesters such as PLA, PBS, PBAT, PHAs, PCL, co- and terpolymers comprising or consisting of lactide, glycolide and caprolactone, starch, modified starch, enzymatically converted starch, polyvinyl alcohol, ethylene vinyl alcohol, modified cellulose, and their mixtures.

Preferably, the first coating contains a binding agent selected from: polyvinyl alcohol, starch, modified starch, enzymatically converted starch, modified cellulose, biodegradable polyesters, and their mixtures. Technical effect of said substances is to achieve good oxygen barrier even without the paper being a high-density paper. Most preferably, the first coating contains at least one of polyvinyl alcohol, modified starch and enzymatically converted starch.

As discussed, the first coating layer can comprise or consist of one or two layers, on one or both sides of the base paper. Preferably, the first coating layer is only on the first side of the base paper 2.

The first coating layer can comprise a layer comprising a binding agent selected from: polyvinyl alcohol, starch, modified starch, enzymatically converted starch, modified cellulose, biodegradable polyesters, and their mixtures. Technical effect of said substances is to improve oxygen barrier properties even without the paper being a high-density paper. Most preferably, the first coating contains at least one of polyvinyl alcohol, modified starch and enzymatically converted starch.

Advantageously, the binding agent of the first coating layer comprises at least 60 wt.% or at least 70 wt.%, more advantageously at least 80 wt.% or at least 90 wt.%, and most advantageously at least 95 wt.% of the above-mentioned substances or consists of the above-mentioned substances. Technical effect is to ensure good surface coverage and film forming for the first coating.

In an embodiment, the binding agent of the first coating layer comprises at least 60 wt.% or at least 70 wt.%, more advantageously at least 80 wt.% or at least 90 wt.%, and most advantageously at least 95 wt.% of polyvinyl alcohol, or consists of polyvinyl alcohol. Technical effect is to provide improved film forming on to the first coating. Another technical effect is to provide improved surface energy level.

Preferably, the binding agent of the first coating layer comprises a total amount of at least 60 wt.% or at least 70 wt.%, more advantageously at least 80 wt.% or at least 90 wt.%, and most advantageously at least 95 wt.% of starch, determined from a total amount of modified starch, and enzymatically converted starch. Technical effect is to provide higher solids content with starches. Another technical effect is to provide cost efficient drying process for the first coating layer. Still another technical effect is to provide environmentally friendly coating having increased biobased content.

In one preferred embodiment, the binding agent of the first coating layer comprises mixtures of PVA and modified starch, and/or enzymatically converted starch.

The first coating can further contain pigments. Mineral pigments can comprise, for example, at least one of: kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulphate, and titanium dioxide. The pigments can comprise at least one platy like pigment like clay.

The first coating layer can comprise mineral pigments in a range between 30 wt.% and 75 wt.%, preferably in a range between 40 wt.% and 70 wt.%, and more preferably in a range between 48 wt.% and 68 wt.%, calculated from the total dry weight of the first coating layer. The usage of the mineral pigments can improve some properties of the material as well as decrease the manufacturing costs of the product. However, the mineral content may not be too high in order to obtain predetermined barrier properties.

Preferably, the main pigment is clay or calcium carbonate, most preferably clay. Technical effect is to provide better immobilization of the binding agent on the surface of the paper and reduce the possibility of the binding agent to enter the micro -and macro pores in the fiber network structure. Thus, the binder can be able to interact better with adjacent coating layers added on the paper substrate with extrusion coating.

Grammage of the support layer 1 , comprising the base paper 2 and the first coating 3, can be 35 to 110 g/m², preferably 38 to 100 g/m², more preferably 42 to 95 g/m², still more preferably 45 to 90 g/m² and most preferably 50 to 85 g/m². Technical effect is to obtain material having good strength properties. Support layer having less grammage is thinner and may have reduced strength properties, but substantially light weight material can decrease manufacturing and transportation costs and reduce environmental load.

Density of the support layer can be equal to or less than 1000 kg/m³, preferably in a range between 800 kg/m³ and 990 kg/m³, more preferably in a range between 820 kg/m³ and 970 kg/m³, still more preferably equal to or less than 950 kg/m³, such as in a range between 850 kg/m³ and 950 kg/m³, still more preferably equal to or less than 940 kg/m³, still more preferably equal to or less than 920 kg/m³, and most preferably equal to or less than 900 kg/m³. Technical effect is to provide environmentally friendly product, wherein energy consumption in the papermaking unit processes, including refining, dewatering, and drying steps, are decreased.

Transparency of the support layer can be below 70%, preferably below 65%, more preferably below 60%, still more preferably below 50%, and most preferably below 45%. Technical effect is to save energy in the paper production due to better dewatering properties.

Gurley Hill air permeability of the support layer can be in a range between 100 and 10 000 s/100ml.

Preferably, Gurley Hill air permeability of the support layer is in a range between 100 s/100 ml and 3000 s/100 ml, more preferably equal to or less than 2 500 s/100 ml, and most preferably equal to or less than 2000 s/100 ml. Technical effect is to provide environmentally friendly product, wherein energy consumption in the papermaking unit processes, including refining, dewatering, and drying steps, is decreased. Surprisingly, the oxygen barrier laminate can be produced even by providing such low Gurley Hill air permeability of the support layer.

Roughness (Bendtsen) of the support layer can be more than 40 ml/min, such as in a range between 60 and 120 ml/min, determined according to standard ISO 2494. Technical effect is that by providing such roughness of the support layer, substrate to be coated with the second coating is smooth. Low amount of surface roughness provides a good substrate for the coating process of the second coating.

The support layer does not need to provide low water vapour transmission rate. In an embodiment, WVTR (23°C /85%RH, ISO 2528) of the support layer is higher than 500 g/m²*day. Technical effect includes improved easiness of the manufacturing process as support layer (at least as such) does not need to provide water vapour barrier material. Furthermore, preferably, mineral oil barrier (HVTR method, Heptane vapour transmission rate) of the support layer is higher than 100 g/m²*day.

Grease barrier (ASTM F119-82, 40C, chicken fat) of the support layer can be less than 2 hours, or even less than 1 hour. Technical effect includes improved easiness of the manufacturing process as support layer (at least as such) does not need to provide grease barrier material.

Oxygen barrier (OTR, 23°C /50%RH, ISO 15105-2) of the support layer can be over 1000 cc/m²*day, or even over 10,000 cc/m²*day. Technical effect includes improved easiness of the manufacturing process as support layer as such does not need to provide oxygen barrier for the material. Another technical effect is to provide environmentally friendly material as biobased materials without high oxygen barrier can be used for the support layer.

As discussed, the first coating layer 3 is preferably only on the first side of the base paper 2. Furthermore, the oxygen barrier material can have one side, i.e., the second side of the base paper, that does not comprise the first coating layer 3 nor the second coating layer 4. In this embodiment, the third coating layer 5 can be applied on the second side of the base paper. The third coating layer 5 can be a surface sizing layer, such as starch based surface sizing layer. The third coating layer 5 can comprise enzymatically converted native starch(es) or other modified starch(es) e.g. such as dextrin(s) or chemically modified starch(es). Thus, the barrier oxygen material can have at least one side, i.e., the first side, having the first and the second coating layers, wherein another side, i.e., the second side, may not be coated, or it can comprise the third coating layer. Most preferably, the second side has only the third coating layer 5 on the base paper 2.

Preferably, the oxygen barrier material has the third coating layer on the second side of the paper, and the third coating layer comprises more than 60 wt.% (by dry weight) starch, more preferably more than 80 wt.% (by dry weight) starch, still more preferably more than 90 wt.% (by dry weight) starch, and most preferably at least 95 wt.% (by dry weight) starch. Advantageously, a grammage of the third coating layer is 0.5-1.5 gsm, more preferably 0.7-1 .3 gsm. Technical effects of the third coating layer include that the starch on the second side facilitates drying of the coating layers, preventing blistering, dusting, deposits and curling of the material. Further technical effects include decreased porosity and improved smoothness of the support layer, and decreased fibre picking tendency in printing.

In an advantageous embodiment, the oxygen barrier material comprises the first coating layer on the first side of the base paper, wherein the first coating layer comprises polyvinyl alcohol and a pigment, preferably kaolin, and the third coating layer on the second side of the base paper, wherein the third coating layer comprises, consists of, or essentially consists of starch.

Technical effects of this combination include that polyvinyl alcohol in the first coating composition improves coating holdout of the subsequent coating layer and improves barrier after barrier coating, and the starch on the second side facilitates drying of the coating layers, preventing blistering, dusting, deposits and curling of the material.

In this advantageous embodiment, the coating composition of the first coating layer preferably comprises polyvinyl alcohol equal to or more than 30 wt.%, more preferably equal to or more than 40 wt.%, such as from 40-60 wt.%, determined from total dry weight of said coating layer, and pigment(s) equal to or more than 30 wt.%, more preferably equal to or more than 40 wt.%, determined from total dry weight of said coating layer.

Further, preferably, the third coating layer on the second side of the base paper comprises starch equal to or more than 60 wt.%, more preferably equal to or more than 80 wt.%, determined from total dry weight of said coating layer on the second side of the paper.

Technical effects of this combination include controlled and efficient drying process, and improved controllability of moisture profile of the oxygen barrier material. Furthermore, this combination can improve printability of the oxygen barrier material and also prevent dusting of the oxygen barrier material, as well as improve surface strength properties of the oxygen barrier material. Further technical effects include decreased porosity and decreased fibre picking tendency in printing.

In an embodiment, the first coating layer is a multilayer structure comprising two or three layers. In this embodiment, the multilayer structure may comprise

1 ) a layer comprising PVA and a pigment, such as kaolin, and

2) a layer comprising a binder and a pigment, such as kaolin, on the previous layer, and

3) an additional layer comprising a binder and a pigment, such as kaolin, on the previous layer.

The multilayer structure of the first coating layer can comprise a layer having a coat weight of 2 to 8 g/m², preferably 5.0 - 6.5 g/m², comprising at least one platy pigment, and 20 to 60 wt.% of poly(vinyl alcohol) (PVA) of the total dry weight of the first coating layer, and another layer(s) each having a coat weight of 4 to 12 g/m², preferably 6.0 - 10 g/m², comprising at least one platy pigment, and 20 to 60 wt.% of binder of the total dry weight of the layer.

However, preferably the first coating layer consist of one coating layer. During experimental tests it was noted that additional layers of tested dispersion coatings did not significantly improve oxygen barrier of the oxygen barrier material.

Second coating layer

The support layer 1 comprises the base paper 2 and the first coating 3. The support layer 1 can be coated with a second coating 8 to obtain an oxygen barrier material 10 comprising the first coating layer 3 and the second coating layer 4.

Preferably, the first coating and the second coating are on the same side of the base paper 2. More preferably, the second coating layer is on the first coating layer. Still more preferably, the second coating layer is directly on the first coating layer. The technical effect is to obtain improved oxygen barrier for the material. Alternatively, there can be another coating layer between the first coating layer 3 and the second coating layer 4, such as a tie layer 6.

Advantageously, the second coating layer 4 comprises or consists of one or more biodegradable materials and partly or fully renewable raw materials, called generally ‘biopolymer’.

The second coating can be based on a polymer. The second coating can be based on at least one of the following polymers and their mixtures: polybutylene succinate, polylactic acid, i.e., polylactide PLA, PLLA, PDLA, PDLLA, and its co- and terpolymers, polycaprolactone PCL, polyester amide PEA, polyhydroxyalkanoate PHA, i.e., PHB, PHBV, PH3B4B, PHBH, polybutyrate styrene PBS, aliphatic aromatic co-polyester AAC, starch-based starch-polymer blends, for example PSM and TPS, which advantageously comprise at least 10 wt.% and not more than 90 wt.% of starch, polybutylene succinate terephthalate, polybutylene adipate terephthalate, and other biopolyesters. The second coating can comprise a blend of above-mentioned polymers.

Preferably, the second coating is based on at least one of the following polymers and their mixtures: polybutylene succinate, polylactic acid, i.e., polylactide PLA, PLLA, PDLA, PDLLA, and its co- and terpolymers, polyhydroxyalkanoate PHA, i.e., PHB, PHBV, PH3B4B, PHBH, aliphatic aromatic co-polyester AAC, starch based starch polymer blends, for example PSM and TPS, which advantageously comprise at least 10 wt.% and not more than 90 wt.% of starch, and polybutylene adipate terephthalate.

More preferably, the second coating is based on at least one of the following polymers and their mixtures: polybutylene succinate, polylactic acid, i.e., polylactide PLA, PLLA, PDLA, PDLLA, lactic acid co- and terpolymers, i.e., Poly(lactide-co-glycolide) (PLGA), Poly(lactide-co-£-caprolactone) copolymer (PLCL) or Poly(lactide-co- glycolide-co-E-caprolactone (PLGCL) polyhydroxyalkanoate PHA, i.e., PHB, PHBV, PH3B4, PHBH, and polybutylene adipate terephthalate.

Preferably, the second coating comprises polybutylene succinate as its main polymer. Technical effect is to provide improved properties such as desired melting point and melt flow rate for extrusion coating process.

Gram mage of the second coating is preferably 5 to 50 gsm, more preferably 8 to 35 gsm, and most preferably 12 to 25 gsm (by dry weight). Technical effect is to provide improved barrier properties for the oxygen barrier material cost- efficiently.

A thickness of the second coating layer can be in a range between 4 pm and 40 pm, preferably between 6 to 35 pm, and more preferably between 8 pm and 30 pm, and most preferably from 10 to 25 pm. Technical effect is to obtain protection from oxygen cost efficiently with the second coating.

The second coating can further comprise one or more additives, such as one or more of slip additive(s), thermal stabilizer(s), anti-block or antistatic agent(s), and UV stabilizer(s), etc. Technical effect of the additive is to modify the surface and/or optical properties of the second coating. Furthermore, the second coating can contain inert raw materials, which can be solid, insoluble additives providing e.g., opacity or color, such as talc, calcium carbonate, titanium dioxide, and/or carbon black. The content of the inert raw materials can be, for example, not higher than 10%, advantageously lower than 5%, more advantageously lower than 2%. In a preferred embodiment, the second coating comprises talc.

The second coating layer can be detached from the oxygen barrier material. Preferably, the second coating layer can be detached from the oxygen barrier material so that less than 5 wt.% of the support layer stays with the second coating layer and less than 5 wt.% of the second coating stays with the support layer. Technical effects include improved recyclability and/or compostability of the oxygen barrier material.

The second coating layer is preferably detached from the oxygen barrier material in order to determine properties from the second coating layer.

The detached second coating layer can have a mineral oil barrier (HVTR method, Heptane vapour transmission rate) less than 10 g/m²*day. Technical effect is to improve mineral oil barrier properties of the obtained oxygen barrier material.

The detached second coating layer can have a grease barrier (ASTM F119- 82, 40°C, chicken fat) less than 36 hours, or less than 30 hours. Technical effect is to provide improved grease barrier properties of the obtained oxygen barrier material.

In an embodiment, the detached second coating layer has WVTR (23°C /85%RH, ISO 2528) value higher than 100 g/m²*day.

Total amount of biopolymers in the second coating layer 4 can be at least 50 wt.%, such as 50 to 100 wt.%, preferably 70 to 99.5 wt.%, and more preferably 80 to 99 wt.% calculated from the total dry weight of the second coating layer. Technical effect is to provide improved amount of biopolymer(s) to fill voids between e.g., pigment particles. Further technical effects include obtaining improved oxygen barrier properties.

A total amount of recycled plastics, preferably biopolymers, in the second coating layer 4 can be 0 to 30 wt.%, more preferably 2 to 20 wt.% calculated from the total dry weight of the second coating layer.

The second coating layer can have an oxygen barrier (OTR, 23°C/50%RH), over 100 cc/m²*day, preferably over 200 cc/m²*day, or over 400 cc/m²*day. Thus, the second coating layer as such may not be capable to provide high oxygen barrier. Technical effect includes improved easiness of the manufacturing process as the second coating layer (at least as such) does not need to provide oxygen barrier properties.

The second layer can comprise only one coating layer, or more than one coating layer. The second coating layer can form the topmost coating layer of the oxygen barrier material. However, there may be, for example, a printing on the second coating layer.

Tie layer

The oxygen barrier material can comprise a tie layer 6. Technical effect of the tie layer 6 is to bond adjacent layers together, and to avoid delamination. The adhesion is preferably selected so that the second coating layer can have a tailored adhesion with the support layer, which is sufficient for processing in converting but enabling (even manual) separation of the support layer and the second coating.

Tie layer 6 can be selected so that the tie layer is compatible with adjacent coating layers.

Some materials may for example be hydrophilic and lose binding on contact with moisture. Suitable polymers for tie layer preferably comprise or consist of polymers with elevated polarity, for example based on maleic anhydride- grafted polyolefins (such as PE or PP), ethylene-vinyl acetate Copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-butyl acrylate copolymer (EBA), or similar polyolefin copolymers, or polyurethane.

The tie layer can be based on a non-reactive tie layer resin, such as an ethylene-vinyl acetate (EVA), ethylene-methyl acrylate (EMA), or ethyleneacrylic acid (EAA), or ethylene-grafted-maleic anhydride, or ethylene methacrylic acid (EMAA).

The tie layer can be based on a reactive tie layer resin, such as anhydride modified polyethylene (AMP). Technical effect is that reactive tie layer resins react with an adjacent layer, forming a strong bond between the layers.

Grammage of the tie layer can be, for example, 0.1 to 5 gsm, more preferably 0.5 to 3 gsm.

Preferably, the second coating layer is directly on the first coating layer, and the oxygen barrier material does not comprise the tie layer. Further, advantageously, the oxygen barrier material does not comprise, e.g., an EVOH based layer. The technical effect is to improve easiness of the manufacturing process of the oxygen barrier material, as well as decrease manufacturing costs as the oxygen barrier properties are obtained without an EVOH layer. Thus, preferably, the oxygen barrier material is EVOH free material. However, it is possible that in an embodiment the oxygen barrier material comprises the EVOH based layer.

Oxygen barrier material

As discussed, the oxygen barrier material has the support layer and the second coating layer on the support layer. Preferably, the first coating and the second coating are on the same side of the base paper, i.e., on the first side of the base paper 2. In this case, the second coating is preferably on top of the first coating.

It is also possible that the first coating and/or the second coating are provided on both sides of the base paper.

The oxygen barrier material can have

- the support layer comprising the paper and the first coating layer, having WVTR value of higher than 500 g/m²*day, and

- the second coating layer on the support layer, having WVTR value of higher than 100 g/m²*day, such as higher than 150 g/m²*day, or higher than 200 g/m²*day wherein the oxygen barrier material can an improved WVTR value (23°C /85%RH, ISO 2528) of less than 100 g/m²*day, typically less than 80 g/m²*day. A technical effect is to provide environmentally friendly material having a good WVTR value by using a support layer and/or the second coating layer having substantially low WVTR value.

The oxygen barrier material can have

- the support layer comprising the paper and the first coating layer, typically having mineral oil barrier evaluated as heptane vapor transmission rate of higher than 20 g/m²*day, and

- the second coating layer on the support layer, typically having heptane vapor transmission rate of higher than 2 g/m²*day, wherein oxygen barrier material can have an improved mineral oil barrier (HVTR method, Heptane vapour transmission rate) of less than 2 g/m²*day. Technical effect is to improve, cost efficiently, mineral oil barrier properties for the obtained oxygen barrier material. Another technical effect is to provide environmentally friendly material as biobased materials without high mineral oil barrier can be used for the layers.

The oxygen barrier material can have

- the support layer comprising the paper and the first coating layer, typically having grease barrier value of less than 2 hours, and

- the second coating layer on the support layer, typically having grease barrier value of less than 36 hours, wherein oxygen barrier material can have a grease barrier value of over 72 hours. Technical effect is to improve, cost efficiently, grease barrier properties for the obtained oxygen barrier material. Another technical effect is to provide environmentally friendly material as biobased materials without high grease barrier can be used for the layers

The oxygen barrier material can have an oxygen barrier value of less than 80 cc/m²*day, preferably less than 50 cc/m²*day, more preferably less than 30 cc/m²*day, and still more preferably equal to or less than 20 cc/m²*day, and most preferably equal to or less than 17 cc/m²*day.

The oxygen barrier material can have

- the support layer having an oxygen barrier value of over 500 cc/m²*day, such as over 2000 cc/m²*day, and

- the second coating layer as such having an oxygen barrier value of over 100 cc/m²*day, such as over 200 cc/m²*day, wherein oxygen barrier material can have an oxygen barrier value of less than 80 cc/m²*day, typically less than 50 cc/m²*day, preferably less than 30 cc/m²*day, and still more preferably equal to or less than 20 cc/m²*day, and most preferably equal to or less than 17 cc/m²*day. Technical effect is to provide improved barrier properties for the oxygen barrier material cost- efficiently. Another technical effect is to provide environmentally friendly material as materials without high oxygen barrier can be used for the layers.

The oxygen barrier material can be heat-sealable. Heat sealability is determined at 0.6 bar sealing pressure, by using 1.0 s dwell time. In an embodiment, the second coating layer is heat sealable, at least, at 160°C (at 0.6 bar sealing pressure and 1 .0 s dwell time). The second coating layer can further be heat sealable at 140°C. Moreover, the second coating layer is preferably heat sealable at 130°C. In a preferred embodiment, the second coating layer is heat sealable, at least, at temperatures from 120°C up to 160°C. Technical effect of the heat sealability is to provide, cost efficiently, good barrier properties over the sealing. The adhesion between the support layer and the second coating can be strong enough to process the oxygen barrier material in converting. During experimental tests, the adhesion value was determined to be 1 in the scale of 1 to 5. The oxygen material was successfully tested in a vertical-form-fill-seal (VFFS) packing machine for the production of pillow bags.

The second coating layer can be detached from the support layer by hand with no significant amounts of fibers or coatings being left to the second coating layer. Preferably, the detached second layer comprises less than 5 wt.% cellulose based fibers and/or the first coating. This is of advantage in recycling, enabling high recycling rates for the support layer to the fiber fraction.

All above disclosed values for the oxygen barrier material can be values of such oxygen barrier material consisting of the support layer and the second coating layer.

The values for the second coating layer can be determined from the second coating layer detached from the oxygen barrier material.

The oxygen barrier material comprises at least the support layer and the second coating layer. In an embodiment, the oxygen barrier material 10 consist of the base paper 2, the first coating layer(s), and the second coating layer(s).

Laminate comprising at least two cellulose fiber based layers

Referring to Figs 2a-b and 3a-b, the support layer and the second coating layer can also be included into a structure that contains at least two cellulose fiber based layers, such as further paper(s) and/or paperboard(s). In this embodiment, a layer of a polymer based coating is preferably left in between each adjacent cellulose fiber based layers.

The support layer and the second coating layer can further be included into at least one of the following laminated structures, as follows: o support layer + second coating layer, o polymer based coating layer + support layer + second coating layer, o polymer based coating layer + coated paperboard + polymer based coating layer + support layer + second coating layer, o polymer based coating layer + coated paperboard + polymer based coating layer + tie layer + support layer + second coating layer, o polymer based coating layer + coated paperboard + polymer based coating layer + coated paper + polymer + support layer + second coating layer, o polymer based coating layer + coated paper + polymer based coating layer + support layer + second coating layer, o polymer based coating layer + coated paper + polymer based coating layer + support layer + second coating layer, o polymer based coating layer + coated paper + polymer based coating layer + tie layer + support layer + second coating layer, o polymer based coating layer + coated paper + polymer based coating layer + support layer + polymer based coating + paper + second coating layer.

Each of said polymer based coating layers can have the same materials and/or properties as the second coating layer.

Each of said coated papers can have the same materials and/or properties as the support layer.

The coating of the coated paperboard(s) and paper(s) can have the same materials and/or the same properties as the first coating.

However, the barrier properties disclosed in this specification can be obtained by using only one support layer and one second coating layer. The laminated structures have at least the same barrier properties as disclosed for the oxygen barrier material.

Method

Figure 4 shows a reduced schematic view of the manufacture of the oxygen barrier material.

A method for manufacturing an oxygen barrier material can comprise supplying the support layer, and applying the second coating on one or both sides of the support layer by an extrusion technique.

The support layer can be made by a paper machine. The base paper 2 is suitably coated by a first coating unit(s) 11 for applying the first coating 7. The first coating unit can be one of a blade coater, flooded nip coating unit, nozzle unit, short retention unit, rod coater, air brush coater, film transfer coater, curtain coating unit, or spray coating unit.

Preferably, the first coating 7 is applied on the first side of the base paper 2 by using a sizer, such as a size press or a film sizer. Preferably, the second side of the base paper is coated by using a sizer, such as a size press or a film sizer.

Most preferably, the first side of the base paper comprising the first coating and the second side of the base paper comprising a third coating, preferably a starch based coating, are coated simultaneously by using a sizer. Technical effect is to improve the production efficiency as the first coating and the starch based coating can be applied by using a single coating device.

In extrusion, the second coating 8 is applied onto the support layer 1 by an extruder 9. Extrusion coating layer can comprise or consist of a single polymer type.

The extruder 9 can be an extrusion, coextrusion, extrusion lamination or a coextrusion lamination device according to the state of art. In extrusion, a polymer in solid state is converted to molten state under compression pressure. The aim of the extrusion is to produce a thin molten film as uniformly as possible and in a controlled manner onto the surface of a running material. In coextrusion, layers of plastic are combined by means of multiple extrusion screws.

Thus, the second coating 8 that contains biopolymer(s) can be applied onto the support layer by using one of extrusion technique, coextrusion technique, extrusion lamination technique, and coextrusion lamination technique.

Experimental tests

Different support layers and second coatings according to the specification were produced and tested.

Example 1

A support layer was PBS-extrusion coated with less than 30 g/m² coat weight of BioPBS (BioPBS FZ79AC). The support layer has the certificate for compostability according to EN 13432. The PBS grade has the certificate ‘OK COMPOST certified by TUV Austria in European Union’. This PBS grade does not provide any oxygen barrier properties. Also, the support layer used does not have any oxygen barrier or mineral oil barrier properties.

Surprisingly the oxygen barrier of the PBS-extrusion coated laminate was ca. 14 cc/m²*day in 23°C/50%RH and mineral oil barrier measured as heptane vapour transmission rate (HVTR) was ca. 2 g/m²*day, which can be seen as extremely good value as HVTR value under 10 g/m²*day is a high performance mineral oil barrier.

Surprisingly, a material with oxygen barrier properties can be created with even a single extrusion coating polymer having no oxygen barrier properties.

Thanks to the novel material, several advantages were obtained, such as a suitable protection from oxygen. The novel material was able to be a part of a protective packaging.

Comparable example

Polyethylene was extrusion-coated on kraft-type paper without intermediate first coating layer. This is a typical structure for barrier materials used for packing. The coating is not biodegradable. The adhesion of the coating to the base paper without precoating was 5 on a scale of 1 to 5, 5 being the strongest.

It was not possible to manually detach the polyethylene layer from the paper (Figure 5b).

Example 2

Adhesion between the support layer and the second coating was tested.

Surprisingly, it was possible to detach the film by hand with no significant amounts of fibers or coatings. The adhesion value was determined to be 1 in the scale of 1 to 5.

The adhesion of the second coating was still strong enough to process the oxygen barrier material in converting. The oxygen material was successfully tested in a vertical-form-fill-seal (VFFS) packing machine for the production of pillow bags. Thus, the first coatings comprising pigments had a tailored adhesion advantageous for recycling, and it was possible to manually detach the PBS layer from the support layer (Figure 5a).

Thanks to the low adhesion between the support layer and the second coating, high recycling rates for the support layer to the fiber fraction was enabled. During experimental tests, less than 5% of the support layer ended up in the reject.

Example 3

The base paper according to this specification was dispersion coated by using water-based dispersions containing pigments and binders as follows:

A) one dispersion coating layer on the base paper (material A, a test point),

B) two dispersion coating layers on the base paper (material B, a comparative example), and

C) three dispersion coating layers on the base paper (material C, a comparative example).

All these materials were further extrusion coated as presented in Example 1 .

The materials A, B and C comprised one coating layer comprising PVA and kaolin. This coating layer was applied by using a sizer.

The materials B and C further comprised another coating layer on the previous layer. Said another coating layer comprised latex and pigment. This coating layer was applied by using a blade coater.

The material C further comprised still another coating layer on the previous layer. This additional coating layer comprised latex and pigment. This coating layer was applied by using a blade coater.

For all materials A to C, the support layer comprised the first coating layer comprising 20 to 60 wt.% of poly(vinyl alcohol) (PVA) of the total dry weight of the coating layer.

The other layer(s) for the materials B and C each had a coat weight of 6.0 - 10 g/m² and comprised at least one platy pigment and 20 to 60 wt.% of latex of the total dry weight of the layer.

During experimental tests it was noted that the above discussed additional dispersion coatings did not significantly improve oxygen barrier of the oxygen barrier material. For example, the oxygen barrier of the materials was between 12 and 17 cc/m2*day in 23°C/50%RH for the tested materials. Thus, the additional dispersion coating with pigment and latex mixture did not give significant benefit in terms of oxygen barrier for the oxygen barrier material presented in Example 1 .

Furthermore, it is to be noted that latexes of the materials B and C were not biodegradable polymeric materials. The invention can be modified within the scope of the appended claims.

Claims

Claims:

1 . A method for manufacturing an oxygen barrier material comprising supplying a support layer (1 ) having a density of equal to or less than

1000 kg/m³, preferably between 800 kg/m³ and 990 kg/m³, the support layer comprising a paper (2) comprising cellulose-containing natural fibres, and a first coating layer (3) on the paper (2), the first coating layer (3) containing a binding agent, wherein a grammage of the first coating layer (3) is in a range between 2 g/m² and 10 g/m², applying a second coating on the support layer (2) by an extrusion technique, thereby forming a second coating layer (4) on the support layer (1 ), a grammage of the second coating layer being in a range between 5 g/m² and 50 g/m², wherein

- the oxygen barrier material (10) is compostable according to standard EN 13432, and

2. An oxygen barrier material comprising a support layer (1 ) having a density of equal to or less than 1000 kg/m³, preferably between 800 kg/m³ and 990 kg/m³, the support layer (1 ) comprising a paper (2) comprising cellulose-containing natural fibres, and a first coating layer (3) on the paper (2), the first coating layer containing a binding agent, wherein a grammage of the first coating layer (3) is in a range between 2 g/m² and 10 g/m², and a second coating layer (4) on the support layer (1 ), a grammage of the second coating layer (4) being in a range between 5 g/m² and 50 g/m², wherein A) - the second coating layer (4) is compostable and/or biodegradable in industrial composting so that it is at least 90% biodegradable in 6 months, determined according to standard EN 13432, and

B) the oxygen barrier material (10) has an oxygen barrier value of less than 70 cc/m²*day, preferably less than 50 cc/m²*day, and more preferably less than 20 cc/m²*day, measured according to ISO 15105-2 at 23°C/50%RH.

3. The method or the oxygen barrier material, wherein the first coating layer (3) and the second coating layer (4) are nanocellulose free coating layers.

4. The method or the oxygen barrier material, wherein the support layer has an oxygen barrier of equal to or more than 500 cc/m²*day, preferably equal to or more than 1000 cc/m²*day, most preferably over 5000 cc/m²*day.

5. The method or the oxygen barrier material, wherein the second coating layer has an oxygen barrier of more than 90 cc/m²*day, preferably equal to or more than 100 cc/m²*day, most preferably over 150 cc/m²*day.

6. The method or the oxygen barrier material, wherein the second coating layer (4) and the first coating layer (3) are on a first side of the paper, and the second coating layer is on the first coating layer.

7. The method or the oxygen barrier material according to claim 6, wherein the oxygen barrier material comprises a third coating layer (5) on a second side of the paper (2), the third coating layer comprising or consisting of starch.

8. The method or the oxygen barrier material according to claim 7, wherein the third coating layer (5) comprises starch equal to or more than 80 wt.%, determined from total dry weight of the third coating layer (5).

9. The method or the oxygen barrier material according to claim 7 or 8, wherein a grammage of the third coating layer is 0.5-1 .5 g/m², preferably 0.7-1.3 g/m².

10. The method or the oxygen barrier material, wherein the second coating layer comprises at least one of polybutylene succinate, polyhydroxyalkanoate, polylactic acid, co- or terpolymer(s) of glycolide and/or lactide, or polybutylene adipate terephthalate, preferably, the second coating layer comprises polybutylene succinate.

11. The method or the oxygen barrier material, wherein the first coating layer contains a binding agent selected from: starch, modified starch, enzymatically converted starch, polyvinyl alcohol, modified cellulose, biodegradable polyesters, and their mixtures, preferably the binding agent is selected from: polyvinyl alcohol, starch, modified starch, enzymatically converted starch, modified cellulose, and their mixtures.

12. The method or the oxygen barrier material, wherein

- the second coating layer has a mineral oil barrier (Heptane vapour transmission rate) of less than 10 g/m²*day, and/or

- the support layer has a mineral oil barrier (Heptane vapour transmission rate) of at least 100 g/m²*day, and/or

- the oxygen barrier material has a mineral oil barrier (Heptane vapour transmission rate) of less than 2 g/m²*day.

13. The method or the oxygen barrier material, wherein

- WVTR value of the support layer is higher than 500 g/m²*day, and/or

- WVTR value of the second coating layer is higher than 100 g/m²*day, and/or

- the oxygen barrier material has a WVTR value of less than 100 g/m²*day, determined at 23°C /85%RH according to standard ISO 2528.

14. The method or the oxygen barrier material, wherein

- the support layer has a grease barrier less than 2 hours, and/or

- the second coating layer has a grease barrier less than 36 hours, and/or

- the oxygen barrier material has a grease barrier over 72 hours, determined according to ASTM F119-82 at 40°C by using chicken fat.

15. The method or the oxygen barrier material, wherein a transparency of the support layer is below 65%, preferably below 50%, determined according to standard DIN 53146.

16. The method or the oxygen barrier material, wherein a Gurley Hill air permeability of the support layer is more than 100 s/100 ml, preferably in a range between 100 s/100 ml and 3000 s/100 ml.

17. The method or the oxygen barrier material, wherein the second coating layer is manually detachable from the support layer.

18. A packaging material or a package comprising the oxygen barrier material according to any of the preceding claims 2 to 17.