WO2024252070A1

WO2024252070A1 - Heat sealable packaging material

Info

Publication number: WO2024252070A1
Application number: PCT/FI2024/050296
Authority: WO
Inventors: Christiane Laine; Kuisma Littunen; Esa SAUKKONEN; Mikko Oksanen; Aleksi PEKKANEN; Leena Kunnas
Original assignee: UPM Kymmene Oy
Current assignee: UPM Kymmene Oy
Priority date: 2023-06-09
Filing date: 2024-06-06
Publication date: 2024-12-12
Anticipated expiration: 2025-12-09

Abstract

The invention relates to a method for manufacturing a heat sealable packaging material (1), the method comprising: supplying a support layer (2b) comprising a paper (2a), applying a first barrier coating composition (7) in form of an aqueous dispersion, thereby forming a first barrier coating layer (4), the first barrier coating layer (4) comprising binding agents at least 45 wt.% of a total dry weight of the first barrier coating layer (4), applying a second barrier coating composition (8), thereby forming a second barrier coating layer (5), wherein the second barrier coating composition (8) comprises dispersed heat sealable polymer(s) at least 45 wt.% of a total dry weight of the second barrier coating layer (5). The invention further relates to a heat sealable packaging material, and a package comprising a heat sealable packaging material, and a use of the heat sealable packaging material (1) in a package.

Description

HEAT SEALABLE PACKAGING MATERIAL

Technical field

The specification relates to a method for manufacturing a heat sealable packaging material. The specification also relates to heat sealable packaging materials.

Background

A large variety of packaging materials is manufactured in industry. 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. Further, packaging materials used for food products must have some properties that may not be needed in other applications.

Materials used for obtaining desired barrier properties can be selected so that if e.g., good water vapor barrier properties are needed, a packaging material can comprise a layer having excellent water vapor barrier properties, e.g., an aluminum foil.

In industry, however, there is still need for new packaging materials.

Summary

It is an aim of this specification to present a heat sealable packaging material. Furthermore, it is an aim of this specification to present a method for manufacturing a heat sealable packaging 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 heat sealable packaging material comprising bio-based and biodegradable binders. The packaging material according to this specification comprises a support layer comprising cellulose-containing natural fibers. The support layer comprising cellulose- containing natural fibers can comprise a paper. The paper can be a viscose free paper, i.e., a paper that does not contain viscose fibers.

The heat sealable packaging material can comprise three coating layers on a first side of a paper, i.e., two barrier coating layers and a first precoating layer. The heat sealable packaging material can further comprise one coating layer on a second side of a paper, i.e., a second pre-coating layer.

The first pre-coating layer is a preferable layer on the first side of the paper, between the uncoated paper and the barrier coating layers.

The second pre-coating layer is an optional but preferable layer on the second side of the paper, such as between the uncoated paper and a printing.

The (optional) pre-coating layer(s) can be directly on the paper, preparing the surface of the support layer for the first barrier coating layer and/or a printing. At least one of the precoating layers can comprise or consist of a binding agent.

Thus, the support layer can be a precoated paper. Preferably, the first barrier coating layer is on the first precoating layer.

The paper can be calendered, such as supercalendered paper. For example, the uncoated paper can be treated by methods such as calendering to enable coating hold-out. Further technical effect is to provide improved barrier properties for the heat sealable packaging material cost-efficiently.

The second barrier coating layer can be on the first barrier coating layer, most preferably directly on the first barrier coating layer. Technical effect is to obtain improved barrier properties for the heat sealable packaging material. Another technical effect is that the second barrier coating layer and the first barrier coating layer create a synergistic effect, further improving barrier properties of the heat sealable packaging material. Still another technical effect is to provide good heat sealability for the heat sealable packaging material. A method for manufacturing a heat sealable packaging material according to this specification can comprise the following steps: supplying a support layer comprising a paper comprising cellulose- containing natural fibres, the support layer further comprising a first precoating layer on a first side of the paper, wherein a grammage of the first precoating layer is in a range between 1 g/m² and 10 g/m² and applying a first barrier coating composition in form of an aqueous dispersion on the first precoating layer, the aqueous dispersion preferably having solids content from 30 to 45 wt.%, thereby forming a first barrier coating layer, the first barrier coating layer having a coat weight of 2 to 10 gsm and comprising binding agents at least 45 wt.% of the total dry weight of the first barrier coating layer, wherein a first binding agent of the first barrier coating composition is selected from starches and hemicelluloses and their mixtures, and the second binding agent of the first barrier coating composition is selected from polyvinyl alcohols, ethylene-vinyl alcohol copolymers, alginates, chitosans, and their mixtures, applying a second barrier coating composition in form of an aqueous dispersion on the first barrier coating layer, thereby forming a second barrier coating layer, the second barrier coating layer having a coat weight of 4 to 12 gsm, the second barrier coating composition comprising dispersed heat sealable polymer(s) at least 45 wt.% of the total dry weight of the second barrier coating layer, wherein the dispersed heat sealable polymer(s) is/are selected from

- acrylates,

- ethylene-acrylic acid copolymers,

- styrene-acrylate copolymers,

- styrene-butadiene copolymers,

- polyolefins,

- polyesters, and

- their mixtures. A heat sealable packaging material according to this specification can comprise a support layer comprising a paper comprising cellulose-containing natural fibres, the support layer further comprising a first precoating layer on a first side of the paper, wherein a grammage of the first precoating layer is in a range between 1 g/m²and 10 g/m² a first barrier coating layer having a coat weight of 2 to 10 gsm and comprising binding agents at least 45 wt.% of the total dry weight of the first barrier coating layer, wherein a first binding agent of the first barrier coating composition is selected from starches and hemicelluloses and their mixtures, and a second binding agent of the first barrier coating composition is selected from polyvinyl alcohols, ethylene-vinyl alcohol copolymers, alginates, chitosans, and their mixtures, and a second barrier coating layer having a coat weight of 4 to 12 gsm and comprising heat sealable polymer(s) at least 45 wt.% of the total dry weight of the second barrier coating layer, wherein the heat sealable polymer(s) is/are selected from acrylates, ethylene-acrylic acid copolymers, styrene-acrylate copolymers, styrene-butadiene copolymers, polyolefins, polyesters, and their mixtures, wherein

- the first precoating layer is situated between the paper and the first barrier coating layer, and

- the first barrier coating layer is situated between the first precoating layer and the second barrier coating layer.

As discussed, the heat sealable packaging material comprises the first precoating layer, which precoating layer is between the paper and the first barrier coating layer. A grammage of the first precoating layer is in a range between 1 gsm and 10 gsm. Preferably, for obtaining all desired properties, hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and starches form at least 70 wt.%, more preferably at least 80 wt.%, still more preferably at least 90 wt.%, and most preferably at least 95 wt.% (by dry weight) of the binding agents of the first barrier coating layer. Therefore, a total amount of hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and starches is preferably at least 70 wt.%, more preferably at least 80 wt.%, still more preferably at least 90 wt.%, and most preferably at least 95 wt.% (by dry weight) determined from a total dry weight of the binding agents in the first barrier coating layer.

The paper can be calendered or supercalendered paper. Technical effect is to provide improved surface, e.g., for barrier coatings.

The first binding agent of the first barrier coating layer can comprise starch, wherein a degree of polymerization of the starch is preferably from 100 to 3000. Technical effects include obtaining desired barrier properties, such as desired grease barrier properties, together with the second binding agent.

Alternatively, or in addition, the first binding agent of the first barrier coating layer can comprise hemicellulose, wherein a degree of polymerization of the hemicellulose is preferably from 50 to 300. Technical effects include obtaining desired barrier properties, such as desired grease barrier properties, together with the second binding agent. Another technical effect is to use biobased raw material that has no nutritional value for food or feed.

The second binding agent of the first barrier coating layer is preferably selected from polyvinyl alcohols and ethylene-vinyl alcohol copolymers. Technical effects of the second binding agent include increasing elasticity of the coating layer.

A ratio of the first binding agent of the first barrier coating layer to the second binding agent of the first barrier coating layer is preferably in a range from 9:1 to 1 :1 , more preferably from 4:1 to 2:1. Technical effects include providing improved barrier properties as well as desired film forming, emulsifying and adhesive properties.

In an advantageous embodiment, the heat sealable polymers are selected from styrene-acrylate copolymers, styrene-butadiene copolymers, and polyolefins, more preferably, the heat sealable polymers are selected from styreneacrylate copolymers and styrene-butadiene copolymers.

Preferably, all coating layers of the heat sealable packaging material are nanocellulose and aluminum free coating layers. Technical effect is to provide cost efficiently environmentally friendly heat sealable barrier material.

Preferably, the paper is a viscose free paper. Technical effect is to provide, cost efficiently, environmentally friendly heat sealable barrier material.

Preferably, the furnish used for the paper is free of highly refined cellulose. Further, the paper is preferably free of highly refined cellulose including nanocellulose. Technical effect is to decrease energy consumption and, hence, provide cost efficiently environmentally friendly heat sealable barrier material.

Preferably, the furnish is free of recycled fibers from used beverage cartons (UBC). Advantageously, the paper is free of recycled fibers from used beverage cartons (UBC). Further, the heat sealable packaging material is preferably free of recycled fibers from used beverage cartons (UBC).

In an embodiment, the first barrier coating layer has a mineral pigment content from 20 wt.% to 65 wt.%, and/or the second barrier coating layer has a mineral pigment content from 10 wt.% to 60 wt.%. Technical effects include decreasing manufacturing costs of the product, while obtaining desired barrier properties. Further, said mineral pigment contents can increase solids content of the barrier coating layer(s).

Preferably, heat sealable packaging material has an oxygen barrier value of less than 1000 cc/m²*day, more preferably less than 700 cc/m²*day, and most preferably less than 400 cc/m²*day.

Preferably, the heat sealable packaging material has a mineral oil barrier (Heptane vapour transmission rate) of less than 20 g/m*day, more preferably less than 15 g/m*day, and most preferably less than 10 g/m*day.

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

Preferably, the heat sealable packaging material has a grease barrier over 60 hours, determined according to ASTM F119-82 at 40°C by using chicken fat.

A package according to this specification can comprise the heat sealable packaging material according to this specification.

Conventionally, a barrier is formed on a fiber-based substrate by using e.g. metallization, extrusion-coating or lamination using plastics. Nowadays producers and end users are looking for alternative paper and board products in various applications on a fit for purpose bases avoiding metallization, extrusion-coating, or lamination.

All coating layers of the heat sealable packaging material are preferably aluminum free. Most preferably, the heat sealable packaging material does not contain a metal-based foil. Technical effect is to obtain environmentally friendly, aluminum free route to obtain desired barrier values.

The heat sealable packaging material according to the specification can be manufactured in an environmentally friendly way. Dispersion-coating offers a route to thinner coating layers compared to extrusion-coating or lamination. Further, dispersion-coatings can reduce manufacturing and transportation costs. This decreases environmental load such as the carbon dioxide load. Thus, preferably, the heat sealable packaging material does not have an extrusion coated layer.

Thanks to the novel heat sealable packaging material, predetermined barrier properties can be obtained in a more environmentally friendly way than conventionally. The heat sealable packaging material can provide excellent grease, mineral oil and water vapor barrier properties for a package made of the heat sealable packaging material. The heat sealable packaging material is capable of preventing or at least limiting water vapor, grease and mineral oil migration through the heat sealable packaging material. Further, the sealable packaging material can be recyclable in a fiber stream according to PTS METHOD PTS-RH 021/97 October 2012, Cat 2.

A total amount of natural and biodegradable polymers in the first barrier coating layer can be at least 50 wt.%, calculated from the total dry weight of the first barrier coating layer.

Preferably, binding agents of the first barrier coating layer are inherently biodegradable so that a biodegradation of the binding agents of the first barrier coating layer as such in water is higher than 50 weight-% in two months, and over 90% in three months, determined according to standard ISO 14851 . Thus, biodegradation of the binding agents as such in water can be higher than 50 weight-% in two months, and over 70% in three months, determined from the binding agents of the first barrier coating layer according to standard ISO 14851. Technical effect is to provide environmentally friendly heat sealable barrier material.

Further, the organic material of the first barrier coating layer can be at least 85 % biodegradable, determined according to ISO 14851. Technical effect is to provide environmentally friendly heat sealable barrier material.

The heat sealable packaging material can have a biodegradable content of at least 30 % determined of total amount of binding agents of the first barrier coating layer and heat sealable polymer(s) of the second barrier coating layer. Technical effect is to provide environmentally friendly heat sealable barrier material.

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

The packaging material according to this specification is preferably used for packaging food. Effective barriers, include resistance to water vapor, grease, oil, mineral oil, and oxygen, are often required in packaging industry to extend shelf-life of packaged food products.

Advantageously, the heat sealable packaging material is heat sealable at least at 150°C, determined at 0.6 bar sealing pressure, by using 1 .0 s dwell time.

More preferably, the heat sealable packaging material is heat sealable at any temperature from 120°C to 160°C, determined at 0.6 bar sealing pressure, by using 1 .0 s dwell time.

Most preferably, the heat sealable packaging material is heat sealable at 150°C, determined at 0.2 bar sealing pressure, by using 0.5 s dwell time.

Technical effect is that ability of the heat sealable packaging material to be heat-sealed in many temperatures and pressures can enhance process flexibility in packaging, thus, it is possible to use, e.g., heat sensible printing.

Brief description of the drawings

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

Figs 1 , 2a-c illustrate an example of heat sealable packaging materials in cross-section,

Fig. 3 illustrates an example of some method steps for manufacturing a heat sealable packaging material, Figs 4-5 show examples of heat sealable packaging materials in crosssection, wherein Fig. 4 shows SEM image of a precoating layer and a first barrier coating layer, and Fig. 5 shows SEM image of a precoating layer, a first barrier coating layer, and a second barrier coating layer,

Fig. 6 discloses seal strength curves from experimental tests after sealing of 15 mm wide specimen of heat sealable packaging materials at 0.2...1.6 bar at 150°C, wherein good sealing properties were demonstrated at all tested sealing pressures, and

Figs 7a-l show test results from packaging trials in a VFFS machine.

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 description

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

1 heat sealable packaging material,

2a paper,

2b support layer,

3 precoating layer,

3a first precoating layer on a first side of the paper 2a,

3b second precoating layer on a second side of the paper 2a,

4 first barrier coating layer,

5 second barrier coating layer,

6 precoating composition,

6a first precoating composition,

6b second precoating composition,

7 first barrier coating composition,

8 second barrier coating composition,

9 calender or precoating unit,

10 first barrier coating unit, and 11 second barrier 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) Cobbeo ISO 535

4) WVTR ISO 2528 at 23°C/50%RH and 23°C/85%RH

5) Oxygen barrier ASTM D3985-05 at 23°C/50%RH

6) Grease barrier ASTM F1 19-82 at 40°C using chicken grease

7) Compostability EN 13432

8) Biodegradability ISO 14851

9) Brookfield viscosity SCAN-P 50:84 using RV Brookfield equipment

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

11 ) Roughness ISO 2494

12) 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. 13) Molecular weight distribution determination for starch:

Agilent 1260 Infinity II multidetector GPC equipment with a PLgel Mixed B set (three analytical columns and one precolumn) are used for measuring starch molecular weight distributions.

Dimethylsulfoxide (DMSO) with 50 mM lithium bromide (LiBr) is used as solvent and eluent. The flow rate is 1 .0 ml/min, and the injection volume is 100 pl. The samples are prepared at a concentration of 5 mg/ml and the samples are filtered using 0.2 pm PTFE syringe filters (PALL Cooperation, Port Washington, NY, USA) before analysis.

The GPC multidetector system includes a refractive index detector (Rl), a viscosity detector (VS) and a dual angle light scattering detector (LS) which has measuring angles 15° and 90°. All the detectors are used together (triple detector calibration) to measure and calculate starch molecular weight distributions using poly(methyl methacrylate) (PMMA) (Polymethylmethacrylate standard, nominal Mp 200,000 g/mol, Agilent Technologies, Inc, Santa Clara, CA, USA) for calibration. Agilent GPC/SEC Software, Version A.02.01 is used for calculating the molecular weight distribution. Molecular weight based on weight (Mw), number (Mn) as well as polydispersity index (PDI) are reported.

14) The melting temperature Tm and glass transition temperature Tg:

The melting temperature Tm and glass transition temperature Tg can be determined by differential scanning calorimetry (DSC) using differential Scanning Calorimeter (Mettler Toledo equipment). The measurements are done under nitrogen flow of 50 ml/min with the following program Dynamic heating rate of 10 °C/min.

1 . Dynamic phase from 0 °C to 110 °C

2. Isothermic phase at 110 °C, 60 min

3. Dynamic phase from 110 °C to 240 °C (First heating)

4. Isothermic phase at 240 °C, 2 min

5. Dynamic phase from 240 °C to 0 °C (First cooling)

6. Isothermic phase at 0 °C, 2 min

7. Dynamic phase from 0 °C to 240°C (Second heating)

8. Isothermic phase at 240 °C, 2 min, and

9. Dynamic phase from 240 °C to 20 °C 15) Recycling tests determining recyclability are determined according to PTS METHOD PTS-RH 021/97 October 2012, Cat 2.

16) Heat sealability test:

Unless otherwise indicated, the heat sealability is tested by cutting 15 x 120 mm specimen from the heat sealable packaging material and sealing them coating vs. coating according to ASTM F2029-16. Seal strength (N/15 mm) can be measured with a tensile tester according to standard ASTM F88/F88M-15.

Further, unless otherwise indicated, sealing parameters are temperature of 150°C, dwell time of 1 .0 s. and jaw pressure of 0.6 bar.

17) Packaging machine testing

Production test run for pillow bags were performed using VFFS machine using serrated jaw profile for the top and bottom seal and flat jaw profile for the longitudinal seal. Seal integrity testing of the produced bags was done visually by evaluating the sealing areas and triple points (i.e., horizontal and longitudinal seal crossing).

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.

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

In this specification, percentage values relating to an amount of a material are percentages by weight (wt.%) unless otherwise indicated. All the contents (percentages) are in dry weight, unless otherwise expressed.

The terms ‘gsm’ refers to grams per square meter (g/m²). Unless otherwise indicated, all the grammages (i.e., coat weights) are in dry weight.

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’.

The term "PVA" refers to polyvinyl alcohol. Polyvinyl alcohol is a synthetic polymer prepared by the polymerization of vinyl acetate, followed by a controlled hydrolysis of the ester in the presence of an alkaline catalyst.

The term “EVOH” refers to ethylene-vinyl alcohol. The ethylene-vinyl alcohol is a copolymer of ethylene and vinyl alcohol. The ethylene-vinyl alcohol can be prepared by polymerization of ethylene and vinyl acetate, followed by hydrolysis.

Hemicellulose is a natural polysaccharide and a major part of lignocellulosic biomass, i.e., a renewable natural polymer. Hemicelluloses can be used for replacing plastic in selected applications such as films and coatings. Thus, hemicelluloses can be used for making environmentally friendly packages. Hemicelluloses can be categorized into xylans, mannans, mixed linkage 0- glucans, and xyloglucans. In an embodiment, the hemicellulose is a water- soluble hemicellulose.

Starch is a natural polysaccharide present e.g. in wheat, tapioca, potato, rice, barley, corn, or pea. In a preferred embodiment, the starch can be dissolved in water.

For barrier-coating purposes, the starch is degraded or converted to obtain solubility and suitable rheological properties. In this specification, the term "starch" particularly refers to starch(es) degraded by chemical, thermal or enzymatic means, which may be referred as dextrin or modified or converted starch. Degraded starch can be industrially dissolved by using equipment such as a jet cooker at temperatures from 120°C-145°C for 1-3 min. Starch can be cooked at dry solids levels up to 38-42%. Low water use and energy saving are achieved at high solids content by reducing evaporative costs. The jet cooker utilizes high velocity steam and turbulent mixing for complete mixing of fluid and steam.

Native starch can be dissolved at high solids content by using starch enzymatic conversion. Alpha-amylase is added to the native starch slurry and the slurry is heated with steam or in heating equipment to 60-85°C for 5-30 minutes dependent on the starch quality. Further heating in e.g. a jet cooker up to 120- 145°C for 1 -3 min is performed to finalize the dissolution and to denaturize the enzymes.

Alternatively, starch can be cooked in batch cooking by adding modified starch to water under stirring and by heating the slurry under stirring to 90-100°C until the starch dissolves, usually in 20-60 minutes.

Native starch can be converted also in the laboratory according to the procedure described above.

Polyvinyl alcohol can be dissolved by adding the polyvinyl alcohol powder or granulates to water and by heating the slurry to 80-100°C for 20-60 minutes using steam or a heating equipment. Fully hydrolyzed PVA usually has a degree of hydrolysis (DS) of 98% to 99.8%, and can dissolve in water only at > 80 °C.

The term “latex” refers to a dispersion of polymer particles in water. Latex may be natural, for example originating from flowering plants, or be synthetic, or the combination thereof.

The term “polymer dispersion” refers to a polymer dispersed into water by a dispersion technology such as a thermal or mechanical method or combinations thereof. The term “dispersible polymer” refers to a polymer that can be dispersed into water by a dispersion technology such as a thermal or mechanical method or combinations thereof.

In this specification, the term “pigment” particularly refers to mineral pigments. Mineral pigments can comprise at least one of: kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulphate, and titanium dioxide.

In this specification the term "platy pigment" refers to pigments having a flat structure in which one dimension is substantially smaller than the two other dimensions of the structure. Examples of platy pigment include kaolin, talc, and mica.

The term “coating composition” refers to an aqueous composition to be applied on to a surface of an object to form a coating layer.

The term "dispersion coating" refers to a coating technique in which a coating composition in form of an aqueous dispersion comprising polymer particles is applied to a surface of a substrate to form a solid coating layer after drying.

The term “coating layer” refers to a thin solid layer that is applied to a surface of a substrate.

The terms “biobased” and “biobased material” refer to materials that are derived from plants and/or other renewable agricultural, marine, and forestry materials, as opposed to non-renewable materials, such as petroleum. In this specification, the terms refer to biobased material by this origin without chemical modification except hydrolysis. An exception is modified starch that may be modified to a low extent, meaning degree of substitution below 0.1. The degree of substitution (DS) refers to the average number of the hydroxyl groups substituted per anhydrous glucose unit (AGU) in starch. Another exception is oxidized starch.

Advantageously, all coating layers of the heat sealable packaging material are formed by the dispersion coating technique. Technical effect is to provide, efficiently, thinner coating layers compared to extrusion-coating or lamination. Further, dispersion-coating can reduce manufacturing and transportation costs. This decreases environmental load such as the carbon dioxide load.

Support layer

The support layer 2b comprises a paper 2a having a first side and a second side. Thus, the support layer 2b has a first side and a second side.

The paper 2a can be a calendered paper. The paper can be a supercalandered paper. Technical effect is to improve smoothness of the paper before applying the barrier coating layers.

The support layer comprises a first precoating layer 3, 3a on the paper 2a. Technical effect is to provide improved surface for the paper before applying the barrier coating layers.

The paper 2a 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 paper 2a comprises cellulose-containing natural fibers which are of wood origin. The paper 2a 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. The chemically pulped natural fibre is also called as a chemical pulp. In an advantageous example, the content of chemically pulped natural fibres in all the cellulose- containing natural fibers used in the paper 2a is thus at least 70 wt.%, at least 80 wt.% or at least 90 wt.%, advantageously at least 95 wt.%, and more preferably at least 98 wt.%. Most preferably, all the cellulose-containing natural fibers used in the paper 2a are chemically pulped cellulose-containing natural fibers.

Preferably, the paper 2a does not contain so-called mechanical pulp.

Preferably, the paper 2a does not contain regenerated fibres or filaments. Thus, advantageously, the heat sealable packaging material is free of regenerated fibres and filaments.

Preferably, the paper 2a does not contain viscose fibers. Thus, the paper is preferably a viscose free paper. Therefore, the heat sealable packaging material is preferably free of viscose. Technical effect is to improve cost efficiency as well as environmental friendliness of the product.

Furthermore, preferably, the paper does not contain synthetic fibres or filaments. Therefore, the heat sealable packaging material is preferably free of synthetic fibres and filaments.

Furthermore, preferably, the paper does not contain highly refined fibers. The paper is also free of recycled fibers from used beverage cartons (UBC).

The paper 2a refers to an uncoated structure, i.e., an uncoated paper.

As discussed, the support layer 2b can have, in addition to the paper 2a, precoating layer(s) 3, 3a, 3b.

Thus, the paper 2a can be coated with precoating composition(s) 6, 6a, 6b. The support layer 2b has at least a first precoating layer 3, 3a on the first side of the paper 2a and, optionally, a second precoating layer 3, 3b on the second side of the paper 2a.

If the support layer 2b comprises the first precoating layer 3a and the second precoating layer 3b, the coating compositions of the first and second precoating layers preferably differ from each other.

As discussed, the support layer comprises at least one precoating layer 3, 3a, 3b. Each precoating layer 3, 3a, 3b can have a grammage in a range between

1 gsm and 10 gsm. Preferably, each precoating layer 3 has a grammage from

2 to 8 gsm, more preferably from 3 to 7 gsm, and most preferably from 4 to 6 gsm. Technical effect is to provide improved surface for the support layer in order to achieve full surface coverage with substantially low coat weight of the precoating. Another technical effect is to prepare the surface of the support layer for barrier coating compositions and to work as an adhesion promoter to the first barrier coating layer.

Thickness of the first precoating layer 3a and/or the optional second precoating layer 3b is preferably between 1 to 10 pm, and more preferably between 2 pm and 8 pm, and most preferably from 3 to 7 pm. Technical effect is to prepare the surface of the support layer 2b (e.g., for barrier coatings) cost efficiently.

The precoating layer(s) 3a, 3b can comprise or consist of a binding agent. The precoating layer(s) can have a binding agent content of at least 25 wt.%, preferably at least 32%, such as in a range between 35% and 60%, and most preferably in a range between 35% and 50%, referring to relative proportion of the binding agent(s) in the total content of the precoating(s).

The binding agent in the precoating layer 3, 3a, 3b can comprise at least 65%, preferably at least 75%, more preferably at least 85%, and most preferably at least 90% of biodegradable material (by dry weight).

The binding agent(s) of the precoating layer 3, 3a, 3b can be selected from: starch, modified starch, enzymatically converted starch, polyvinyl alcohol, ethylene vinyl alcohol, modified cellulose, dispersions of different polyesters such as PLA, PBS, PBAT, PHAs, PCL, co- and terpolymers comprising or consisting of lactide, glycolide and caprolactone, and their mixtures.

Advantageously, the binding agent(s) of the precoating layer 3, 3a, 3b 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 precoating.

In an embodiment, the binding agent(s) of the first precoating layer 3, 3a comprises polyvinyl alcohol and/or modified starch and/or enzymatically converted starch, a total amount being 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.%, up to 100 wt.%. Technical effect is to ensure good surface coverage and to provide improved film forming on to the precoating.

The precoating layer 3, 3a, 3b can further contain pigments. The precoating layer 3, 3a, 3b can contain mineral pigments, such as 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 pigment like clay.

The precoating layer 3, 3a, 3b 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 precoating layer 3. The usage of the mineral pigments can improve some properties of the material, improve the rheological properties in the coating process, as well as decrease the manufacturing costs of the product. However, the mineral content may not be too high.

Preferably, the binding agent(s) of the second precoating layer 3b comprises or consists of modified starch and/or enzymatically converted starch, a total amount of modified starch and enzymatically converted starch preferably being 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.%, up to 100 wt.%. Technical effect of the second precoating layer 3b is to improve the printability of the heat sealable packaging material. As discussed, the second precoating layer 3b can contain pigments. Technical effect of pigments is to provide improved surface for printing.

The first side of the paper 2a can be coated with a first precoating composition 6a for obtaining the first precoating layer 3a.

In addition, the second side of the paper 2a can be coated with a second precoating composition 6b for obtaining the second precoating layer 3b.

Thus, the support layer 2b comprises the first precoating layer 3a on the first side of the paper 2a. The support layer 2b can further comprise the second precoating layer 3b on the second side of the paper 2a.

Preferably, the support layer 2b comprises only one precoating layer 3, 3a, 3b on one or both sides of the paper 2a.

Grammage of the support layer 2b is advantageously at least 35 gsm, more advantageously at least 40 gsm and preferably not greater than 130 gsm. The grammage of the support layer 2b may be, for example, in a range between 40 gsm and 120 gsm. In an advantageous example, the grammage of the support layer 2b is between 45 gsm and 110 gsm. Technical effect is to obtain heat sealable packaging material having good strength properties. Support layer 2b 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. Thus, it is possible to provide good barrier, heat sealability and strength properties while the heat sealable packaging material can be environmentally friendly solution due to the minimum amount of raw materials needed for the package.

Density of the support layer 2b can be from 800 to 1200 kg/m³. Technical effect is to provide support layer that either through high density and/or by a coating layer provides good coating hold out. In an embodiment, density of the support layer 2b is less than 1000 kg/m³, more preferably in a range between 800 kg/m³ and 990 kg/m³, still more preferably in a range between 820 kg/m³ and 970 kg/m³, and most preferably equal to or less than 950 kg/m³, such as in a range between 850 kg/m³ and 950 kg/m³. Technical effect is to provide particularly environmentally friendly product, wherein energy consumption in the papermaking unit processes, including refining, dewatering, and drying steps, are decreased.

In another embodiment, density of the support layer is at least 1000 kg/m³, such as in a range between 1000 kg/m³ and 1200 kg/m³, more preferably in a range between 1020 kg/m³ and 1170 kg/m³, and most preferably in a range between 1050 kg/m³ and 1150 kg/m³. Technical effect is that high-density paper structure enables good interaction between the surface of the support layer and a coating layer added on the support layer.

Roughness (Bendtsen) of the support layer 2b can be more than 40 ml/min, such as in a range between 60 ml/min and 120 ml/min, determined according to standard ISO 2494. Technical effect is that by providing such roughness of the support layer 2b, substrate to be coated with the barrier coating is smooth. Low amount of surface roughness provides a good substrate for the coating process of the first barrier coating composition.

Due to the barrier coating layers, support layer 2b does not need to provide low water vapour transmission rate. In an embodiment, WVTR (23°C /85%RH, ISO 2528) of the support layer 2b is higher than 500 g/m²*day. Technical effect includes improved easiness of the manufacturing process as the support layer 2b (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 2b is higher than 100 g/m²*day. Technical effect includes further improved easiness of the manufacturing process as the support layer 2b (as such) does not need to provide mineral oil barrier.

Grease barrier (ASTM F119-82, 40°C, chicken fat) of the support layer 2b can be less than 2 hours, or even less than 1 hour. Technical effect includes improved easiness of the manufacturing process as support layer 2b (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 2b 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 2b 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 2b.

First barrier coating layer

The heat sealable packaging material 1 comprises the first barrier coating layer 4. The technical effect of the first barrier coating layer 4 is to prepare the foundation for oxygen and grease barrier properties.

The first barrier coating composition 7 contains two or more binding agents. Thus, the first barrier coating layer contains a first binding agent and a second binding agent.

The first barrier coating layer 4 can have a binding agent content of at least 45 wt.%, preferably at least 50%, such as in a range between 55% and 80%, and most preferably in a range between 58% and 75%, referring to relative proportion of binding agents in the total content of the first barrier coating layer.

The first binding agent can comprise or consist of polysaccharide(s).

The polysaccharides can include, for example, hemicelluloses, starches, carboxymethylcelluloses, and other cellulose ethers or esters.

Preferably, the first binding agent(s) of the first barrier coating composition include(s) hemicellulose(s) and/or starch(es). The first binding agent(s) can include at least one of a water-soluble hemicellulose and a water-soluble starch. Preferably, the binding agents of the first barrier coating composition comprise starch(es) and/or hemicellulose(s). A total amount of starches and hemicelluloses can be up to 90 % (by dry weight) of the binding agents of the first barrier coating composition.

In an embodiment, the first binding agent of the first barrier coating layer comprises one or more hemicelluloses, which can include arabinoxylan or galactoglucomannan isolated from wood meal or sawmill chips directly or after preparation of holocellulose.

In an embodiment, the first binding agent of the first barrier coating layer comprises hemicellulose(s), and the weight average molecular weight of the hemicellulose(s) is preferably in the range of 10 000-30 000 g/mol, measured according to Escalante et al., Carbohydrate Polymers 87(4), 2012. Technical effect is improved film formation in coatings.

In an embodiment, the first binding agent of the first barrier coating layer can comprise one or more starches. The starches can include modified, thermally modified and enzymatically modified starches such as depolymerized starch molecules such as dextrins, enzymatically converted starch (depolymerized starch), maltodextrins and pyrodextrins and cross-linked starches or thinned, oxidized, esterified, etherified, or acetylated starches. Technical effect of said substances is to achieve desired solubility, tailored rheology, and good barrier properties.

Preferably, the first binding agent of the first barrier coating layer contains or consists of at least one of modified starch and enzymatically converted starch.

In an embodiment, the first binding agent of the first barrier coating layer comprises starch, the starch being based on a dextrin. Technical effect is to provide substantially high solids content in coating composition and excellent basis for grease resistance. In addition, the starch can be easily dissolved e.g. by Jet or batch cooking.

In one embodiment, the starch is based on enzymatically converted native starches. Technical effect is to provide substantially high solids content in coating composition, lower price compared to modified starches, possibility to tailor the viscosity and solids content in the coating composition preparation and excellent basis for grease resistance.

In one embodiment, the starch comprises or is an oxidized starch, i.e., a starch obtained by treating a starch with oxidants such as hypochlorite or hydrogen peroxide. The technical advantage is introduction of anionic charge.

In one embodiment, the enzymatic conversion of starch is performed using alpha-amylase(s). Technical effect is to decrease the molecular weight to a level that results in favorable viscosity ranges of the dissolved starch at solids contents of higher than 30%, such as higher than 32%, or higher than 33 %.

The starch material may be from any source including, for example, wheat, tapioca, potato, rice, barley, corn, or pea.

The starches, if used in the first barrier coating composition 7, preferably have a degree of polymerization from 100 to 3000, more preferably from 200 to 1500. Technical effect is that the degree of polymerization is low enough to achieve solids content up to 33-42 weight-% while the degree of polymerization remains high enough for obtaining desired barrier properties, such as desired grease barrier properties, together with the second binding agent.

The hemicelluloses, if used in the first barrier coating composition 7, preferably have a degree of polymerization from 50 to 300, more preferably from 70 to 200. Technical effect is that the degree of polymerization is low enough to achieve solids content in the hemicellulose solution higher than 20% while the degree of polymerization remains high enough for obtaining desired barrier properties, such as desired grease barrier properties, together with the second binding agent.

In a preferred embodiment, the starch is a low molecular weight starch material having a weight average molecular weight (Mw) from 15 000 to 500 000 g/mol, more preferably from 30 0000 to 400 000 g/mol, still more preferably from 40 000 to 300 000 g/mol, and most preferably from 50 000 to 250 000 g/mol. The low molecular weight starch material is preferably selected from dextrins, and native starches having tailored molecular weight. A layer comprising starch in the first barrier layer - particularly when comprising dextrins and/or enzymatically degraded native starches - has provided very good performance during experimental tests. Another technical effect is that the molecular weight is low enough to achieve solids content in the starch solution up to 33-42 weight-% while maximizing the grease barrier of the coating layer.

The binding agents of the first barrier coating layer 4 can comprise at least 30 wt.%, preferably from 30 wt.% to 95 wt.%, more advantageously at least 50 wt.% and less than 90 wt.%, and most advantageously at least 66 wt.% and less than 85 wt.% of starches or hemicelluloses. Technical effects include improved cost efficiency and runnability as well as an excellent viscosity compared to using the second binding agent alone. Another technical effect of starches is to provide higher solids content for the first barrier coating layer and, hence, to provide cost efficient drying process. Still another technical effect is to provide environmentally friendly coating having increased biobased content and introducing a chemical that is biodegradable in many environments including soil, fresh water, and marine water.

In addition to the first binding agent of the first barrier coating layer, the binding agents of the first barrier coating layer comprises a second binding agent.

The second binding agent is preferably selected from polyvinyl alcohols, ethylene-vinyl alcohol copolymers, alginates, chitosans and their mixtures, more preferably the second binding agent is selected from polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures. Technical effect is to provide bio-compatible, odorless, and non-toxic material having improved film forming properties, particularly suitable for foodstuff packaging. Another technical effect is the inherent biodegradability. Thus, preferably, the first barrier coating layer 4 contains a first binding agent selected from hemicelluloses and starches, and their mixtures, and a second binding agent selected from polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures. Technical effect of this combination is to provide desired biodegradability of the first barrier coating layer. Another technical effect is to create desired grease and oxygen barrier. Still another technical effect is to provide bio-compatible, odorless, and non-toxic material having improved film forming properties suitable e.g. for foodstuff packaging.

The second binding agent of the first barrier coating composition 7 can comprise or consist of polyvinyl alcohol(s) and/or ethylene-vinyl alcohol copolymer(s). The binding agents can comprise polyvinyl alcohol(s) and/or ethylene-vinyl alcohol copolymer(s) from 5 to 50 weight-%, preferably from 10 to 40 weight-%, more preferably from 15 to 35 weight-%, determined of total amount of binding agents. Technical effects include improved film formation properties.

The polyvinyl alcohol(s), if used, can have a degree of hydrolysis in a range from 97 to 100 mol%, and weight average molecular mass from 30 to 60 kDa. Technical effects include a low tendency for foaming and to increase the crystallinity compared to lower degree of hydrolysis.

The ethylene-vinyl alcohol copolymer(s), if used, can have a degree of hydrolysis in a range from 97 to 100 mol-%, weight average molecular mass from 30 to 60 kDa, and ethylene content in a range from 1 to 20 mol-%, preferably from 10 to 15 mol-%. Technical effect is to provide higher hydrophobicity, improved resistance to high humidity, and higher flexibility for the heat sealable packaging material.

The binding agents of the first barrier coating layer can comprise at least 5 wt.% and less than 50 wt.%, more advantageously at least 10 wt.% and less than 40 wt.%, and most advantageously from 15 wt.% to 35 wt.% of polyvinyl alcohol. Technical effect is to increase the elasticity of the coating layer while keeping the biobased content of the coating layer as high as possible.

Preferably, the first barrier coating layer 4 contains

- a first binding agent selected from: modified starches, enzymatically converted starches, hemicelluloses, and their mixtures, and

- a second binding agent selected from polyvinyl alcohols and ethylenevinyl alcohol copolymers, and their mixtures. Technical effect, particularly together with the molecular weights according to this specification, is to maximize solids content compared to levels possible for polyvinyl alcohol or ethylene vinyl alcohol approved as food contact material alone; and simultaneously maximizing the biobased content to the coating layer by the first binding agent. In addition, the presence of the second binding agent increases the elasticity of the coating layer compared a layer consisting exclusively of the first binding agent.

Preferably, hemicellulose(s), polyvinyl alcohol(s), ethylene-vinyl alcohol copolymer(s), and starch(es) form at least 70 wt.%, more preferably at least 80 wt.%, still more preferably at least 90 wt.%, and most preferably at least 95 wt.% (by dry weight) and up to 100 wt.% of the binding agents of the first barrier coating. Technical effect is good basis for grease barrier and possibility to tailor the viscosity of the coating color.

Most advantageously, polyvinyl alcohol(s) and starch(es) form at least 70 wt.%, more preferably at least 80 wt.%, still more preferably at least 90 wt.%, and most preferably at least 95 wt.% (by dry weight) of the binding agents of the first barrier coating. Technical effect is to assure high biobased and inherently biodegradable binding agents.

Preferably, the binding agents of the first barrier coating layer 4 are inherently biodegradable. Inherent biodegradability refers to a biodegradation of the binder as such in water to a level higher than 50 weight-%, preferably > 60%, more preferably > 70% in two months, and over 70%, preferably >80%, more preferably >85% and most preferably >90% in three months, determined according to standard ISO 14851 .

Ratio of the first binding agent to the second binding agent is preferably in a range from 9.5:1 to 0.5:1 , more preferably from 7:1 to 0.8:1 , still more preferably from 5:1 to 1 :1 , and most preferably from 4:1 to 2:1. Technical effects include providing improved barrier properties as well as excellent film forming, emulsifying and adhesive properties.

Further, technical effect of higher starch content is to provide higher solids content as well as higher biobased content for the heat sealable packaging material, and technical effect of higher PVA content is to provide higher elasticity giving an advantage in mechanical processing.

Advantageously, solids content of the first barrier coating composition 7 is from 30 to 45 wt.%, preferably 32-43 wt.%, more preferably 34-41 wt.%. Technical effects include accelerated production efficiency and reduced energy required to dry the applied coating. This solids content can be particularly easily obtained by using said ratio of the first binding agent to the second binding agent.

The first barrier coating layer can further contain one or more mineral 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 first barrier coating layer 4 can comprise mineral pigments in a range between 20 wt.% and 65 wt.%, preferably in a range between 25 wt.% and 60 wt.%, and more preferably in a range between 30 wt.% and 55 wt.%, calculated from the total dry weight of the first barrier coating layer 4. 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 of the first barrier coating layer is talc, clay, or calcium carbonate, more preferably clay or talc, and most preferably kaolin. Technical effect is to provide better immobilization of the binding agent on the surface of the support layer 2b 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 substrate. Another technical effect is to improve runnability of the manufacturing process, and to obtain higher solids content cost efficiently.

The first barrier coating composition and the first barrier coating layer preferably comprises the binding agents and the mineral pigments in a dry weight ratio from 0.8:1 to 6:1 , more preferably from 1.3:1 to 4:1 , and most preferably from 1.5:1 to 3:1. Technical effect is tailoring the rheological properties and decreasing the costs of chemicals.

The first barrier coating composition and the first barrier coating layer 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 first barrier coating layer.

The first barrier coating composition 7 and, hence, the first barrier coating layer, can comprise a plasticizer, which is a compound or composition capable of imparting plasticity flexibility to the heat sealable packaging material. In an embodiment, the plasticizer is selected from the group consisting of glycol, glycerol, sorbitol, glucose, and mixtures thereof.

Total amount of natural and biodegradable polymers in the first barrier coating layer 4 can be at least 50 wt.%, such as 54 to 85 wt.%, preferably 58 to 75 wt.%, and more preferably 60 to 70 wt.% calculated from the total dry weight of the first barrier coating layer 4. Technical effect is to provide biopolymer(s) to fill voids between e.g., pigment particles. Further technical effects include obtaining improved barrier properties.

Grammage of the first barrier coating layer is preferably 2 to 10 gsm, more preferably 3 to 9 gsm, and most preferably 4.5 to 7.5 gsm (by dry weight). Technical effect is to provide improved barrier properties for the heat sealable packaging material cost-efficiently.

A thickness of the first barrier coating layer 4 can be in average in a range between 1 .5 pm and 10 pm, preferably between 3 to 9 pm, and more preferably between 4 pm and 8 pm, and most preferably from 4.5 to 7 pm. Technical effect is to obtain protection from oxygen and grease cost efficiently with the first barrier coating. Another technical effect is that first barrier coating layer 4 and the second barrier coating layer create a synergistic effect providing barrier properties for the heat sealable packaging material. The first barrier coating composition 7 can have a Brookfield viscosity of 100- 1500 mPas, preferably 200-1100 mPas, more preferably 300-900 mPas when measured at 40°C, 100 rpm, at solids contents of 32-40%. Technical effect is that the viscosity is suitable for pumping coating color to the storage tank and the coating units.

Second barrier coating layer

The heat sealable packaging material 1 comprises a second barrier coating layer 5.

One technical effect of the second barrier coating layer 5 is to provide improved water vapor barrier properties. Another technical effect is to provide heat sealability for the heat sealable packaging material 1. Still another technical effect of the second barrier coating layer according to this specification is boosting grease barrier of the heat sealable packaging material by filling possible pinholes. Yet another technical effect of the second barrier coating layer according to this specification is to improve the cracking resistance of the barrier coating layers of the heat sealable packaging materials 1 .

The support layer 2b can be coated with a first barrier coating composition 7 and a second barrier coating composition 8 to obtain the heat sealable packaging material 1 comprising the first barrier coating layer 4, and the second barrier coating layer 5.

The heat sealable packaging material 1 comprises the first precoating layer 3a, the first barrier coating layer 4, and the second barrier coating layer 5 on the same side of the paper 2a. Preferably, the first barrier coating layer 4 is on the first precoating layer 3 and the second barrier coating layer 5 is on the first barrier coating layer 4. The first barrier coating layer 4 can be directly on the first precoating layer 3 and the second barrier coating layer 5 can be directly on the first barrier coating layer 4. The technical effect is to obtain improved barrier properties for the heat sealable packaging material. The second barrier coating layer 5 can comprise one or more heat sealable polymers. Preferably, the second barrier coating layer 5 comprises 20 to 60 wt.% of heat sealable polymer(s) of the total dry weight of the second barrier coating layer 5. Technical effect is to provide heat sealability together with improved barrier properties.

The second barrier coating layer 5 can comprise at least one latex and/or another polymer dispersion-based barrier coating that shows heat sealable properties.

Preferably, the second barrier coating composition 8 is based on latex. Preferably, the second barrier coating layer 5 comprises 20 to 60 wt.% of latex of the total dry weight of the second barrier coating layer 5. Technical effect is to provide improved barrier properties as well as excellent runnability and high- solid content capacity.

Latex, if used, can be a natural latex or a synthetic latex, or mixture thereof. Natural latex has better stretching effect, lower tearing strength, mechanical strength, and biodegradable, while synthetic latex, for example styrenebutadiene latex or styrene-acrylate latex, can be produced on a large scale and its cost is typically lower.

In another embodiment, the polymer dispersion comprises polymers such as polyolefins or polyesters with suitable thermal behavior. The technical effect is that the selected polymer is capable of forming an improved barrier layer on a surface of a paper at typical process temperatures on paper machines.

The heat sealable polymer(s) can comprise at least one of the following polymers and their mixtures: acrylates(s), ethylene-acrylic acid copolymer(s), styrene-acrylate copolymer(s), styrene-butadiene copolymer(s), polyolefins, and polyesters. Technical effect is to provide water vapor barrier properties and heat sealability for the heat sealable packaging material.

Preferably, the heat sealable polymer(s) comprise(s) at least one of the following polymers and their mixtures: acrylates(s), styrene-acrylate copolymer(s), styrene-butadiene copolymer(s), and polyolefins.

Technical effects include providing water vapor barrier, improving grease barrier, providing at least moderate oxygen barrier, and providing heat sealability for the heat sealable packaging material.

Most preferably, the heat sealable polymer(s) comprise(s) at least one of the following polymers and their mixtures: acrylates(s), and styrene-acrylate copolymer(s).

Technical effects include providing water vapor barrier, improved grease barrier, at least moderate oxygen barrier, and heat sealability for the heat sealable packaging material, without e.g. polyolefins.

Thus, the second barrier coating layer 5 can comprise one or a blend of above- mentioned heat sealable polymers. Technical effects include providing water vapor barrier, improved grease barrier and heat sealability as well as at least a moderate oxygen barrier.

The dispersed heat sealable polymers, such as latex or polymeric material, as such favorably have a melting temperature in a range between 60°C and 120°C and a glass transition temperature at equal to or below 23°C. This enables film formation in suitable temperature range for drying in paper machines while avoiding blocking. Conventionally, some challenges have been caused due to an absence of web cooling devices at most paper machines. Thus, paper web temperature at a pope reeler of a paper machine is typically around 40°C to 60°C. Therefore, the coating layer on a paper web should not be tacky at this temperature, because otherwise it may cause reel blocking. Thanks to the novel solution, tackiness of the barrier coating can be avoided at a pope reeler.

The second barrier coating layer can comprise 3 to 35 wt.%, preferably 5-30 wt. %, and most preferably from 10 wt.% to 25 wt.% waxes. The wax(es), if used, can comprise at least one of bio-based waxes such as bees wax, carnauba wax, rice bran, rye bran wax, sunflower oil wax, soy wax, bio-based or synthetic Fischer-Tropsch waxes, and synthetic waxes such as paraffin or polyethylene waxes.

Technical effect is to provide improved properties such as the targeted water vapor barrier level. Blending the polymer with a wax can modify the physical properties and particularly hydrophobic properties of the coating layer.

The term “soy wax” refers to natural wax derived from soybeans.

Preferably, the wax(es), if used, are selected from bio-based waxes such as bees wax, carnauba wax, rice bran, rye bran wax, sunflower oil wax, soy wax, and bio-based Fischer-Tropsch waxes.

Technical effect of said waxes is to maintain the desired properties while increasing the biobased content.

The second barrier coating composition and hence the second barrier coating layer 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 additives is to modify the surface and/or optical properties of the second barrier coating layer.

Furthermore, the second barrier coating composition 8 can contain solid, insoluble pigments, providing e.g., opacity or color, such as talc, calcium carbonate, and/or titanium dioxide.

In an embodiment, the second barrier coating layer comprises one or more mineral pigments selected from kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulphate, and titanium dioxide. The second barrier coating layer 5 can comprise mineral pigments in a range between 10 wt.% and 60 wt.%, preferably in a range between 15 wt.% and 50 wt.%, and more preferably in a range between 18 wt.% and 40 wt.%, calculated from the total dry weight of the second barrier coating layer 5. It is of advantage to add filler for rheological properties and also for cost reasons. Pigments allow also higher solids contents and therefore reduce energy consumption in the drying section. Pigment addition in the second coating is also favorable to maintain recyclability of the heat seal material. Further, surprisingly, the second barrier coating layer with said pigment addition to the selected polymer materials shows suitable heat sealability properties for the use in packaging lines.

Thus, the second barrier coating composition 8 can contain at least one platy pigment, preferably talc and/or kaolin. As discussed, the platy pigment refers to pigments having a flat structure in which one dimension is substantially smaller than the two other dimensions of the structure. The platy pigment can be selected from kaolin, talc, and mica. Technical effect of the combination of heat sealable polymers, such as latex(es), and platy pigment(s) is to further enhance the water barrier and water vapour resistance properties. The second layer, if comprising latex and platy pigment, provides excellent water barrier and moisture barrier especially in high humidity, and therefore when applying the coated paper in packaging product to be stored and/or delivered to places with high humidity, for example in the humid subtropical climate region, the packed product is protected well from the moisture outside.

In a preferred embodiment, the second barrier coating layer comprises talc.

In a preferred embodiment, the second barrier coating layer comprises kaolin.

Advantageously, second barrier coating layer 5 comprises kaolin at least 50 wt.%, preferably at least 60 wt.%, more preferably at least 70 wt.%, and most preferably at least 90 wt.%, calculated from all mineral pigments in the second barrier coating layer 5. Kaolin can be easily dispersed into water, improving easiness of the manufacturing process while providing advantages of platy pigments. Grammage of the second barrier coating layer is preferably 3 to 12 gsm, more preferably 4 to 10 gsm, and most preferably 4.5 to 8 gsm (by dry weight). Technical effect is to provide improved barrier properties for the heat sealable packaging material cost-efficiently.

A thickness of the second barrier coating layer 5 can be in a range between 2 pm and 10 pm, preferably between 3 pm and 9 pm, more preferably between

4 pm and 8 pm, and most preferably from 4.5 to 7 pm. Technical effect is to obtain good level of grease and water vapor resistance as well as at least a moderate protection from oxygen cost efficiently with the second barrier coating.

Total amount of heat sealable polymers in the second barrier coating layer 5 can be at least 40 wt.%, such as 40 to 95 wt.%, preferably 50 to 90 wt.%, and more preferably from 55 to 85 wt.%, and most preferably from 60 to 80 wt.%, calculated from the total dry weight of the second barrier coating layer 5. Technical effects include filling voids between particles and obtaining improved barrier properties. Further technical effect is to provide heat sealability.

The second barrier coating layer 5 can form the topmost barrier coating layer of the heat sealable packaging material. Thus, the second barrier coating layer

5 can form the topmost coating layer of the heat sealable packaging material.

In an embodiment, there may be a printing on the second barrier coating layer 5.

In a preferred embodiment, the heat sealable packaging material has the barrier coatings on the first side of the support layer, and the second precoating layer 3b, preferably designed for printing, on the second side of the paper 2a.

Heat sealable packaging material

As discussed, the heat sealable packaging material has the support layer 2b, the first barrier coating layer 4, and the second barrier coating layer 5. Preferably, the first barrier coating layer 4 is situated between the support layer 2b and the second barrier coating layer 5, and the second barrier coating layer 5 is on top of the first barrier coating layer 4.

The heat sealable packaging material can have at least one side, and preferably only one side, that comprises the first barrier coating layer 4 and the second barrier coating layer 5. Preferably, the heat sealable packaging material has the barrier coatings 4, 5 only on first side of the support layer 2b. Technical effect is to decrease environmental load, such as the carbon dioxide load, and to provide cost efficiently environmentally friendly heat sealable barrier material.

The other side of the heat sealable packaging material may only have, for example, the second precoating layer 3b. However, it is also possible that the first barrier coating layer 4 and/or the second barrier coating layer 5 are provided on both sides of the support layer 2b.

The second precoating layer 3b can be a surface size layer. The second precoating layer 3b can consist of one or more binding agents. Alternatively, the second precoating layer can comprise binding agent(s) and pigments.

Therefore, the second side of the support layer can be uncoated, such as calendered, or coated.

If the heat sealable packaging material has a coating layer on the second side of the paper 2a, the coating layer on the second side of the paper 2a is preferably the second precoating layer 3b.

The heat sealable packaging material can have at least one side designed for printing. The printable side(s) is/are preferably printable by using at least one of

® digital printing, such as digital inkjet printing,

« flexography,

® rotogravure, and

• offset lithography. Thus, preferably, the heat sealable packaging material is printable heat sealable packaging material. Technical effect is to improve easiness of printing process for packages comprising the heat sealable packaging material.

In an advantageous embodiment, the heat sealable packaging material comprises the barrier coating layers 4, 5 on the first side of the support layer, and the second side of the support layer comprises a printing. In this embodiment, the second side of the support layer preferably comprises the second precoating 3b on the paper 2a, which second side of the support layer is preferably configured to be printable as such. Technical effect is that the barrier layers can provide suitable barrier properties for a package having the barrier layers on the first side of the support layer, while the printing on the other side of the package can provide information for a user of the package. Alternatively, the second precoating 3b can be configured to be overprinted with a pigment coating, and a printing.

The heat sealable packaging material can have the support layer 2b comprising the paper 2a, the first barrier coating layer 4 comprising a first binding agent, preferably selected from starches and hemicelluloses and their mixtures, and a second binding agent, preferably comprising PVA and/or EVOH, and the second barrier coating layer 5, preferably comprising dispersible heat sealable polymer.

A technical effect is to provide environmentally friendly heat sealable packaging material having good barrier properties.

Thus, the heat sealable packaging material con comprise two barrier layers, wherein the first barrier layer can provide foundation for grease resistance and barrier against oxygen, and the second barrier layer can provide water vapor barrier and enhance the grease and oxygen barrier properties.

Thanks to the novel heat sealable packaging material, there is no need to use extrusion-coated or laminated layer, nor metal layers, for the barrier properties. The heat sealable packaging material is preferably suitable for recycling in a fiber stream according to PTS METHOD PTS-RH 021/97 October 2012, Cat 2.

Further, when contaminated with food residues, the heat sealable packaging material is preferably suitable for composting and/or being burnt after usage, without causing environmental problems.

In this specification, the term “polymeric binders” refers to the binding agents of the first barrier coating layer and the heat sealable polymer(s) of the second barrier coating layer.

The heat sealable packaging material preferably comprises at least 30 % biodegradable polymeric binders, more preferably at least 40 % biodegradable polymeric binders, and most preferably at least 50 % biodegradable polymeric binders, determined from a total amount of the polymeric binders in the first and second barrier coating layers, related to reference material biodegradability, determined according to ISO 14851.

In total, organic material of the first barrier coating layer is preferably at least 85 % biodegradable, more preferably at least 90 % biodegradable, and most preferably at least 93 % biodegradable, related to reference material biodegradability, determined according to ISO 14851.

The polymeric binders preferably comprise at least 20 % biobased binders, more preferably at least 30 % biobased binder, and most preferably at least 40 % biobased binders, determined from total amount of polymeric binders, i.e., the binding agents of the first barrier coating layer and heat sealable polymer(s) of the second barrier coating layer.

As discussed, the term “biobased” means “derived from plants and other renewable agricultural, marine, and forestry materials”. Further, the term “biobased” refers by this origin without chemical modification except hydrolysis. An exception is modified starches that may be modified to a low extent, meaning degree of substitution below 0.1. The degree of substitution (DS) refers to the average number of the hydroxyl groups substituted per anhydrous glucose unit (AGU) in starch.

The heat sealable packaging material preferably comprises less than 80 %, more preferably less than 70 %, and most preferably less than 60 % fossilbased polymeric binders, determined as dry weight of all polymeric binders of the heat sealable packaging material.

The manufacturing process according to this specification can be a lot simplified compared to conventional manufacturing processes. Often a support layer is transported from a paper mill to a converter who adds barrier materials, for example by extruding plastic on paper, as the extruder is not necessarily available at the paper mill, and then coated paper is again transported to another converter/printer for finalizing it into a final product. In the method according to this specification, the barrier coating layers can be done at the paper mill, or at only one converter/printer’s premises, and thus at least one converter step and transportation phase can be avoided, so that the whole process of manufacturing is more efficient.

The heat sealable packaging material can provide a combination of barrier properties against grease and water vapor for foldable or flexible packaging products, which have been difficult to obtain conventionally (without metal foils and laminated films), particularly for foldable or flexible packaging products.

Furthermore, particularly if a starch at high consistency is used for the first barrier coating layer 4 and a latex or polymer dispersion is used for the second barrier coating layer 5, a decreased time for drying can be achieved which consequently facilitates the manufactural efficiency, in particular together with the addition of pigments.

The heat sealable packaging material can have a WVTR value of less than 100 g/m²*day, determined at 23°C /85%RH according to standard ISO 2528. Technical effect is to provide, cost efficiently, desired water vapour barrier properties for the obtained heat sealable packaging material. Another technical effect is to provide environmentally friendly material comprising biobased materials. The heat sealable packaging material can have an improved mineral oil barrier (HVTR method, Heptane vapour transmission rate) of less than 20 g/m*day, more preferably less than 15 g/m*day, and most preferably less than 10 g/m*day. Technical effect is to improve, cost efficiently, mineral oil barrier properties, hence, avoid a risk of mineral oil contamination when using the packaging material e.g. for food. Mineral oil barrier of the heat sealable packaging material can be particularly useful for food products. Another technical effect is to provide environmentally friendly material as materials which do not comprise laminated films or aluminum layers can be used for the heat sealable packaging material.

The heat sealable packaging material can have a grease barrier over 60 hours, determined according to ASTM F119-82 at 40°C by using chicken fat. Technical effect is to provide, cost efficiently, grease barrier properties for the heat sealable packaging material. Another technical effect is to provide environmentally friendly material as materials which do not comprise laminated films or aluminum layers can be used for the heat sealable packaging material.

The heat sealable packaging material can have an oxygen value of less than 1000 cc/m²*day, more preferably less than 700 cc/m²*day, still more preferably less than 500 cc/m²*day, still more preferably less than 300 cc/m²*day, and most preferably less than 100 cc/m²*day. Technical effect is to provide oxygen barrier properties for the heat sealable packaging material cost-efficiently. Another technical effect is to provide environmentally friendly material as materials which do not comprise laminated films or aluminum layers can be used for the heat sealable packaging material.

The heat sealable packaging material is preferably heat sealable according to the heat sealability test. As discussed, the heat sealability is tested by cutting 15 x 120 mm specimen from the heat sealable packaging material and sealing them coating vs. coating according to ASTM F2029-16. In this application, the term “heat sealable” particularly refers to a seal strength (N/15 mm) of at least 3 N/15mm, preferably over 4 N/15mm, or more preferably over 5 N/15mm, measured with a tensile tester according to ASTM F88/F88M-15. Heat sealability can be determined at 0.6 bar sealing pressure (i.e., jaw pressure), by using 1.0 s dwell time. Thus, the heat sealable packaging material is preferably heat sealable at 150°C by using jaw pressure of 0.6 bar and dwell time of 1 .0 s.

The heat sealable packaging material according to this specification is preferably heat sealable at 150°C by using reduced jaw pressure of 0.2 bar and reduced dwell time of 0.5 s. Furthermore, the heat sealable packaging material can be heat sealable at 160°C by using jaw pressure of 0.2 bar and dwell time of 0.5 s.

The heat sealable packaging material can further be heat sealable at 140°C by using jaw pressure of 0.2 bar and dwell time of 0.5 s. The heat sealable packaging material is preferably heat sealable at 130°C by using jaw pressure of 0.2 bar and dwell time of 0.5 s. Technical effect is to provide cost efficiently good barrier properties over the sealing. Additionally, low sealing times for achieving heat sealability can enhance process efficiency in packaging.

Furthermore, the heat sealable packaging material is preferably heat sealable at 150°C by using any jaw pressure from 0.2 bar to 1 .6 bar, and any dwell time from 0.5 s to 1 .0 s.

In a preferred embodiment, the heat sealable packaging material is heat sealable, at least, at temperatures from 120°C up to 160°C. One technical effect of the heat sealability is to provide, cost efficiently, good barrier properties over the sealing. Furthermore, ability of the heat sealable packaging material 1 to be heat-sealed in all temperatures from 120°C up to 160°C can enhance process flexibility in packaging, thus, it is possible to use e.g. heat sensible printing or e.g. use the package comprising the heat sealable packaging material for a heat sensible product.

In an embodiment, the heat sealable packaging material 1 consist of the support layer, the first barrier coating layer, and the second barrier coating layer, at least essentially. Thanks to the heat sealable packaging material, oxygen, mineral oil, and water vapor barrier can be substantially improved, compared to conventional environmentally friendly heat sealable materials. Further, the heat sealable packaging material can have good seal ability so that good barrier properties can be provided over the sealing cost efficiently.

Manufacturing method

A method for manufacturing a heat sealable packaging material can comprise the following steps: providing a support layer 2b comprising a paper 2a and a first precoating layer 3a on the paper 2a, applying a first barrier coating composition 7 onto the support layer 2b in a form of an aqueous dispersion, thereby forming a first barrier coating layer 4, and applying a second barrier coating composition 8 onto the first barrier coating layer 4 in a form of an aqueous dispersion, thereby forming a second barrier coating layer 5.

The support layer 2b can be made by a paper machine. The support layer 2b may be calendered.

The paper 2a is suitably coated by a precoating unit for applying the precoating composition(s) 6, 6a, 6b. The precoating 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.

The first barrier coating composition 7 can be applied onto the support layer 2b by a first barrier coating unit 10 for applying the first barrier coating composition 7. The first barrier coating composition 7 can be applied in the form of an aqueous composition. The first barrier coating unit 10 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. The second barrier coating composition 8 can be applied by a second barrier coating unit 11 for applying the second barrier coating. The second barrier coating composition 8 can be applied in the form of an aqueous composition. The second barrier coating unit 11 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.

Package

Packages can be produced from the heat sealable packaging material.

A package can comprise, essentially consist of, or consist of the heat sealable packaging material. In an embodiment, the heat sealable material forms more than 50 wt.%, such as at least 60 wt.% (by dry weight) of a package.

A package can comprise the heat sealable material, for example, in a laminate structure with another paper or film, or other papers or films.

Thus, in an embodiment, the heat sealable packaging material is used in a packaging laminate construction.

The packages can be produced with packaging machinery intended for flexible packaging. Such packaging machinery can include Form-Fill-Seal (FFS) Machines producing packages in either vertical or horizontal orientation, pouch-making machines, lidding machines, and sealing and overwrapping machines.

Person skilled in the art fully understands that several different packaging formats can be produced with these packaging machinery types.

Experimental tests

Example 1

Starch samples were prepared by conventional cooking of a modified starch (starch 1 ) or by enzymatic conversion of native wheat starch (starch 2 and 3). The molecular weight distributions of the starch samples are shown in Table 1 by describing average molecular weights and the polydispersity.

Table 1. Molecular weight distributions data and viscosity of tested starch samples.

Example 2

Coating compositions were prepared in batch mixers for pilot trials. The coating compositions properties are shown in Table 2.

Table 2. Coating compositions properties

The solids contents of starch-containing coating compositions were all higher than 30% and resulting in a Brookfield viscosity range (100 rpm) of 300-600 mPas in most cases. Even 38.3% solids content was demonstrated. There is still room for using higher solids content as viscosity levels in the range of OOZOO mPas are possible. This is of advantage compared to the solids content range possible for reference coating compositions in which PVA is the only binder, shown here for 25.2% solids content. The selection of PVA’s suitable for products compatible with food contact material approval is limited. This restricts the use of PVA to qualities with a higher viscosity. All listed coating compositions were suitable for blade coating in the pilot coating machine. The use of substantial proportions of modified or enzymatically converted starch together with PVA is thus of advantage in terms of solids content which in turn defines either achievable coat weight or energy consumption in drying.

Comparative example 1

Pilot tests coating trials were performed on a paper substrate with precoating comprising a binder and a platy pigment.

The first barrier coating comprised starch samples from Example 1 , polyvinyl alcohol (hydrolysis degree of 98%), and platy pigment in different ratios. The applied coat weights, water absorption (Cobbeo), water vapor transmission rate (WVTR), grease resistance and heptane transmission rate (HVTR) were measured for all trial points (Table 3). Oxygen transmission rate (OTR) was measured for selected trial points.

Table 3. Trial point descriptions and barrier properties of paper with precoating and first barrier coating.

¹ Water absorption measured as Cobb 60s value at 50% relative humidity and 23°C, standard ISO 535

² Water vapor transmission rate at 50% or 85% relative humidity and 23°C, standard ISO 2528

³ Oxygen transmission rate at 50% relative humidity and 23°C, standard ASTM D3985-05

⁴ Grease resistance at 40°C using chicken grease, standard ASTM F119-82

⁵ Heptane transmission rate at 50%relative humidity and 23°C, according to method described above

The paper coated with first precoating and first barrier coating shows improved barrier properties against grease and an OTR level below 376 cc/(m² d), at best 175 cc/(m² d). All samples showed an excellent mineral oil barrier measured as heptane vapor transmission rate (HVTR). HVTR values below 70 g are expected to correlate with values below the migration limit of 0.5 mg/kg for dry foods with a low fat/oil content (< 4% fat/oil).

However, the water vapor barrier performance suffers at higher humidity (50 versus 85% humidity). In addition, with the structure with precoating and first barrier coating on the paper, no heat seal properties are obtained. The grease resistance was not superior for PVA compared to starch/PVA mixtures with up to 80 w-% starch as binder.

Example 3

The samples from the trial points in comparative example 1 were overcoated in pilot scale using a coating composition comprising a latex, natural-based wax, and a pigment. The applied coat weights, water absorption (Cobbeo), water vapor transmission and grease resistance were measured for all trial points (Table 4). Oxygen transmission rate was measured for selected trial points.

Table 4. Trial point descriptions and barrier properties of paper with first precoating, first barrier coating, and second barrier coating.

¹ water absorption measured as Cobb 60s value at 50%relative humidity and 23°C, standard ISO 535

² Water vapor transmission rate at 85% relative humidity and 23°C, standard ISO 2528 ³ Oxygen transmission rate at 50% relative humidity and 23°C, standard ASTM

D3985-05

⁴ Grease resistance at 40°C using chicken grease, standard ASTM F119-82

The paper coated with first precoating, first barrier coating and second barrier coating shows further improved barrier properties against grease reaching values of > 5 days compared to maximum of 3.6 days without second barrier coating or 1.9 days for the reference with precoating and second barrier coating only. The OTR level remained below 310 cc/(m² d), being below 200 cc/(m²d) for several trial points and improved for the reference with precoating and second barrier coating only. All samples showed an excellent mineral oil barrier measured as heptane vapor transmission rate (HVTR). The water vapor barrier performance at 85% humidity was significantly improved by the second barrier coating reaching values below 90 (m²d). The second barrier coating also introduced heat sealability.

The values were obtained for up to 80% starch as binder in first barrier coating and even with pigment content of 41 % in first barrier coating.

Example 4

The materials of example 3 were tested for heat sealability (paper samples with first precoating and first and second barrier coatings). The maximum force at tear and adhesive is shown in Table 5.

Table 5. Heat sealability of heat sealable packaging material (paper with first

Drecoating, first barrier coating and second barrier coating).

The heat sealability of the heat sealable packaging material is on an excellent level with high seal strength and good adhesion. All sealed samples showed full fiber tear in visual evaluation of the sealing area.

Example 5 The content of biobased binders and biodegradable binders from Example 3 is shown for the tested trial points in Table 6.

Table 6. Biobased and biodegradable contents in the first and second barrier coating layers of the heat sealable packaging material.

¹ Content of biobased binder w-%/w-% of total binder in first and second barrier coating; biobased refers here to starch and/or biobased wax.

Minimum content - no biobased content in the second barrier coating Maximum content - 20% biobased content in second barrier coating

² Content of biodegradable binder w-%/w-% of total binders in first and second barrier coating.

Minimum content - no biodegradable content in the second barrier coating Maximum content - 20% biodegradable content in the second barrier coating

The biobased and biodegradable binder content of all polymeric binders in the first and second barrier coating was evaluated.

The content of biobased material - in the examples starch and biobased wax

- was in all cases except the PVA reference higher than 25%, in many trial points with good barrier properties higher than 35% and in several trial points cases higher than 45%. The advantage of high starch content in the first barrier coating enables significant increase in biocontent in the barrier layers of the heat sealable material.

The content of biodegradable material - in the starch, PVA and biobased wax

- was in all cases higher than 41%, in many trial points with good barrier properties higher than 50% and in several trial points cases higher than 60%. The introduction of substantial proportions of biodegradable binders to the barrier layer was demonstrated. Example 6

The recyclability of the heat sealable packaging material (with first precoating and first and second barrier coatings from Example 3) was tested according to PTS Method PTS-RH 021/97, October 2012. The testing results are compiled in Table 7.

Table 7. Recycling test results for the heat sealable packaging material. Trial point numbers according to Example 3.

The heat sealable packaging material was classified as recyclable according to PTS Method PTS-RH 021/97, October 2012. The screening residue was below 1 w-%:

Example 7 Packaging trials with the heat sealable packaging material (with first precoating and first and second barrier coatings from Example 3) was performed with a commercial vertical-form-fill-seal (VFFS) machine without any machinery modifications.

The operating window for the VFFS machine was determined based on the results obtained from laboratory heat-seal tests (Example 4).

For the experiments, the selected heat-sealing temperature ranged from 100 to 160 °C for the horizontal seal and 100 to 180 °C with the longitudinal seal for the pillow bag type packaging. Dwell times used were of 0.15s, 0.3s, 0.5s, 0.7s, and 1.0s and 0.3s, 0.5s, 0.7s, 1.0s, and 1.5s for the horizontal and longitudinal seal, respectively.

Seal integrity testing of the produced bags was done visually by evaluating the sealing areas and triple points (i.e. horizontal and longitudinal seal crossing). The testing results from packaging trials in the VFFS machine are shown in Figures 7a-l. Fully colored areas with black in Figures 7a-l denote the operating window of samples.

Figures 7a-b show test results from reference points, i.e., the sample -013. Figures 7c-d show test results from sample -015. Figures 7e-f show test results from sample -017. Figures 7g-h show test results from sample -019. Figures 7i-j show test results from sample -021. Figures 7k-l show test results from sample -047.

Based on VFFS machine testing it is possible to produce airtight packages with pillow bag format from the heat-sealable packaging material according to this specification.

The invention is not limited solely to the examples presented in Figures and the above description, but it may be modified within the scope of the appended claims.

Claims

Claims:

1. A method for manufacturing a heat sealable packaging material (1 ) comprising supplying a support layer (2b) comprising a paper (2a) comprising cellulose-containing natural fibres, the support layer (2b) further comprising a first precoating layer (3a) on a first side of the paper (2a), wherein a grammage of the first precoating layer (3a) is in a range between 1 g/m² and 10 g/m², and applying a first barrier coating composition (7) in form of an aqueous dispersion on the support layer (2b), the aqueous dispersion preferably having solids content from 30 to 45 wt.%, thereby forming a first barrier coating layer (4), the first barrier coating layer (4) having a coat weight of 2 to 10 g/m² and comprising binding agents at least 45 wt.% of a total dry weight of the first barrier coating layer (4), wherein a first binding agent of the first barrier coating composition (7) is selected from starches and hemicelluloses and their mixtures, and a second binding agent of the first barrier coating composition (7) is selected from polyvinyl alcohols, ethylene-vinyl alcohol copolymers, alginates, chitosans, and their mixtures, applying a second barrier coating composition (8) in form of an aqueous dispersion on the first barrier coating layer (4), thereby forming a second barrier coating layer (5), the second barrier coating layer (5) having a coat weight of 4 to 12 g/m², the second barrier coating composition (8) comprising dispersed heat sealable polymer(s) at least 45 wt.% of a total dry weight of the second barrier coating layer (5), wherein the dispersed heat sealable polymer(s) is/are selected from

- acrylates,

- ethylene-acrylic acid copolymers,

- styrene-acrylate copolymers,

- styrene-butadiene copolymers,

- polyolefins,

- polyesters, and their mixtures.

2. A heat sealable packaging material (1 ) comprising

A) a support layer (2b) comprising a paper (2a) comprising cellulose- containing natural fibres, the support layer (2b) further comprising a first precoating layer (3a) on a first side of the paper (2a), wherein a grammage of the first precoating layer (3a) is in a range between 1 g/m² and 10 g/m², and

B) a first barrier coating layer (4) having a coat weight of 2 to 10 g/m² and comprising binding agents at least 45 wt.% of total dry weight of the first barrier coating layer (4), wherein a first binding agent of the first barrier coating composition (7) is selected from starches and hemicelluloses and their mixtures, and a second binding agent of the first barrier coating composition (7) is selected from polyvinyl alcohols, ethylene-vinyl alcohol copolymers, alginates, chitosans, and their mixtures, and

C) a second barrier coating layer (5) having a coat weight of 4 to 12 g/m² and comprising heat sealable polymer(s) at least 45 wt.% of total dry weight of the second barrier coating layer (5), wherein the heat sealable polymer(s) is/are selected from acrylates, ethylene-acrylic acid copolymers, styrene-acrylate copolymers, styrene-butadiene copolymers, polyolefins, polyesters, and their mixtures, wherein

- the first precoating layer (3a) is situated between the paper (2a) and the first barrier coating layer (4), and

- the first barrier coating layer (4) is situated between the first precoating layer (3a) and the second barrier coating layer (5).

3. The method according to claim 1 or the heat sealable packaging material according to claim 2, wherein a total amount of hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and starches is at least 70 wt.%, more preferably at least 80 wt.%, still more preferably at least 90 wt.%, and most preferably at least 95 wt.% (by dry weight) determined from a total dry weight of the binding agents in the first barrier coating layer.

4. The method or the heat sealable packaging material according to any of the preceding claims, wherein the support layer (2b) further comprises a second precoating layer (3b) on a second side of the paper (2a), a grammage of the second precoating layer (3b) being in a range between 1 g/m² and 10 g/m².

5. The method or the heat sealable packaging material according to any of the preceding claims, wherein the second binding agent is selected from polyvinyl alcohols and ethylene-vinyl alcohol copolymers.

6. The method or the heat sealable packaging material according to any of the preceding claims, wherein the first binding agent comprises the starch, and a degree of polymerization of the starch is from 100 to 3000.

7. The method or the heat sealable packaging material according to any of the preceding claims, wherein the first binding agent comprises the hemicellulose, and a degree of polymerization of the hemicellulose is from 50 to 300.

8. The method or the heat sealable packaging material according to any of the preceding claims, wherein a ratio of the first binding agent to the second binding agent is in a range from 9.5:1 to 1 :1 , preferably from 4:1 to 2:1.

9. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable polymer(s) is/are selected from styrene-acrylate copolymers, styrene-butadiene copolymers, and polyolefins, preferably, the heat sealable polymer(s) is/are selected from styreneacrylate copolymers and styrene-butadiene copolymers.

10. The method or the heat sealable packaging material according to any of the preceding claims, wherein all coating layers of the heat sealable packaging material (1 ) are nanocellulose and aluminum free coating layers.

11 . The method or the heat sealable packaging material according to any of the preceding claims, wherein the first barrier coating layer (4) has a mineral pigment content from 20 wt.% to 55 wt.%, and/or the second barrier coating layer (5) has a mineral pigment content from 10 wt.% to 55 wt.%.

12. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable packaging material (1 ) has an oxygen barrier value of less than 1000 cc/m²*day, more preferably less than 700 cc/m²*day, and most preferably less than 500 cc/m²*day, determined at 23°C/50%RH according to standard ASTM D3985-05.

13. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable packaging material (1 ) has a mineral oil barrier, determined as heptane vapour transmission rate according to the specification, of less than 20 g/m*day, more preferably less than 15 g/m*day, and most preferably less than 10 g/m*day.

14. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable packaging material (1 ) has a water vapour barrier value of less than 100 g/m²*day, determined at 23°C and 85% RH according to standard ISO 2528.

15. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable packaging material (1 ) has a grease barrier over 60 hours, determined according to standard ASTM F1 19-82 at 40°C by using chicken fat.

16. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable packaging material (1 ) is heat sealable at 150°C, determined by using 1 .0 s dwell time at 0.6 bar sealing pressure, and/or the heat sealable packaging material (1 ) is heat sealable at 150°C determined by using 0.5 s dwell time at 0.5 bar sealing pressure.

17. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable packaging material (1 ) is recyclable in a fiber stream according to PTS METHOD PTS-RH 021/97 October 2012, Cat 2.

18. The method or the heat sealable packaging material according to any of the preceding claims, wherein biodegradation of the binding agents as such in water is higher than 50 weight-% in two months, and over 70% in three months, determined from the binding agents of the first barrier coating layer (4) according to standard ISO 14851 .

19. The method or the heat sealable packaging material according to any of the preceding claims, wherein total amount of natural and biodegradable polymers in the first barrier coating layer (4) is at least 50 wt.%, calculated from the total dry weight of the first barrier coating layer.

20. The method or the heat sealable packaging material according to any of the preceding claims, wherein the barrier coating layers (4,5) has a biodegradable content of at least 30 %, determined of total amount of binding agents of the first barrier coating layer and heat sealable polymer(s) of the second barrier coating layer.

21 . The method or the heat sealable packaging material according to any of the preceding claims, wherein organic material of the first barrier coating layer is at least 85 % biodegradable, determined according to ISO 14851 .

22. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable packaging material is a viscose free material.

23. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable packaging material is free of regenerated fibres and filaments.

24. The method or the heat sealable packaging material according to any of the preceding claims, wherein the furnish used for the paper is free of highly refined cellulose.

25. The method or the heat sealable packaging material according to any of the preceding claims, wherein the paper is free of recycled fibers from used beverage cartons (UBC).

26. A package comprising the heat sealable packaging material (1) according to any of the preceding claims 2 to 25, such as a package comprising a laminate construction comprising the heat sealable packaging material (1 ) according to any of the preceding claims 2 to 25.

27. A use of the heat sealable packaging material (1 ) according to any of the preceding claims 2 to 25 in a package, preferably in a laminate construction of a package.