Heat sealable packaging material

Abstract

The invention relates to a heat sealable packaging comprising a paper (2a), a first precoating layer (3), a barrier-supporting coating layer (4) having a coat weight of 2 to 15 g / m2, and a barrier coating layer (5) having a coat weight of 3 to 12 g / m2 and comprising heat sealable polymer(s) at least 40 wt.% of total dry weight of the barrier coating layer (5). The invention further relates to a method for manufacturing a heat sealable packaging material (1). The invention further relates to a package comprising a heat sealable packaging material. The invention further relates to a use of a heat sealable packaging material (1) in a flexible package. The invention further relates to a use of a barrier-supporting coating layer for lowering a sealing temperature of a heat sealable packaging material.

Description

[0001] HEAT SEALABLE PACKAGING MATERIAL

[0002] Technical field

[0003] The specification relates to a method for manufacturing a heat sealable packaging material. The specification also relates to heat sealable packaging materials.

[0004] A large variety of packaging materials is manufactured in industry. For packaging materials, properties and desired shelf life of products to be packaged typically determine the packaging material used for packaging each product.

[0005] 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. Further, materials used for obtaining desired heat sealability and barrier properties can be selected so that an outermost coating layer is heat sealable. Further, heat sealable packaging materials used for food products must have some properties that may not be needed in other applications.

[0006] In industry, however, there is still need for new heat sealable packaging materials.

[0007] It is an aim of this specification to present a heat sealable packaging material. Further, it is an aim of this specification to present a method for manufacturing a heat sealable packaging material. It is an aim of this specification to present a flexible package. Further, it is an aim of this specification to present a use of a heat sealable packaging material in flexible packaging.

[0008] 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.

[0009] This specification provides a solution for obtaining an improved heat sealable packaging material. 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 heat sealable packaging material can comprise at least two coating layers on a first side of a paper, i.e., a barrier-supporting coating layer and a barrier coating layer. Advantageously, the heat sealable packaging material comprises three coating layers on the first side of the paper, i.e., a first precoating layer, the barrier-supporting coating layer, and the barrier coating layer.

[0010] The heat sealable packaging material according to this specification comprising a barrier-supporting layer comprising a mixture of latex and nonthermoplastic binder, such as water-soluble polymer, has improved heat sealability, i.e., decreased heat sealing temperature. Surprisingly, by using the barrier-supporting coating layer according to this specification instead of other kind of coating layers, e.g., a coating layer wherein binder is consisting of latex, the obtained product had, during experimental tests, at least a 10 degree lower sealing temperature.

[0011] Thus, one unexpected technical effect of using the barrier-supporting coating layer according to this specification is that heat sealability of the barrier coating layer can be substantially improved.

[0012] The heat sealable packaging material comprises the first precoating layer on the first side of a paper. The first precoating layer is a preferable layer on the first side of the paper, between the uncoated paper and the barrier coating layers. A grammage of the first precoating layer is preferably in a range between 1 g / m2and 10 g / m2. The first precoating layer can be directly on the paper. Technical effect of the precoating layer is to prepare the surface of the support layer for the barrier-supporting coating layer.

[0013] The heat sealable packaging material can further comprise a second precoating layer on a second side of the paper. The second precoating layer is an optional but preferable layer on the second side of the paper. The second precoating layer can be situated between the paper and a printing. The second precoating layer can be directly on the paper, preparing the surface of the support layer for a printing. The second precoating layer can comprise or consist of a binding agent.

[0014] Thus, the support layer can be a precoated paper. Preferably, the barriersupporting coating layer is directly on the first precoating layer.

[0015] The paper can be calendered, such as supercalendered paper. The paper can be calendered before or after applying the first precoating layer. Thus, the paper can be treated by methods such as calendering to improve coating holdout. The barrier coating layer can be on the barrier-supporting coating layer. One technical effect is to provide good barrier properties for the heat sealable packaging material.

[0016] Most preferably, for substantially improving heat sealability of the heat sealable packaging material, the barrier coating layer is directly on the barriersupporting coating layer. Surprisingly, the barrier coating layer and the barriersupporting coating layer create such a synergistic effect that heat seal properties of the heat sealable packaging material are improved.

[0017] Surprisingly, during experimental tests, the barrier-supporting coating layer comprising the non-thermoplastic binder, when situated under the barrier coating layer, was able to improve heat seal properties of the heat sealable packaging material compared to a barrier-supporting layer without nonthermoplastic binder. Further, the heat sealable packaging material according to this specification had, during experimental tests, better barrier properties than e.g. materials having two barrier coating layers according to this specification without the barrier-supporting coating layer.

[0018] A method for manufacturing a heat sealable packaging material according to this specification can comprise the following steps: supplying a support layer comprising or consisting of 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, and a grammage of the support layer is preferably in a range between 35 g / m2and 130 g / m2, and applying a barrier-supporting coating composition in form of an aqueous dispersion on the support layer, the aqueous dispersion preferably having solids content from 45 wt.% to 62 wt.%, or from 48 wt.% to 58 wt.%, thereby forming a barrier-supporting coating layer, the barrier-supporting coating layer having a coat weight of 2 to 15 g / m2, preferably 3-12 g / m2and comprising binding agents at least 20 wt.% of the total dry weight of the barrier-supporting coating layer, wherein a first binding agent of the barrier-supporting coating composition is selected from non-thermoplastic polymers, preferably from starches, hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures, and the second binding agent of the barrier-supporting coating composition is selected from styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, and their mixtures, wherein a ratio of the first binding agent to the second binding agent is preferably from 0.5:1 to 5:1 , more preferably at least 1.1 :1 , applying a barrier coating composition in form of an aqueous dispersion, thereby forming a barrier coating layer, the barrier coating layer having a coat weight of 3 to 12 gsm, the barrier coating composition comprising dispersed heat sealable polymer(s) at least 40 wt.% of the total dry weight of the barrier coating layer, wherein the dispersed heat sealable polymer(s) is / are selected from

[0019] - acrylates,

[0020] - ethylene-acrylic acid copolymers,

[0021] - styrene-acrylate copolymers,

[0022] - styrene-butadiene copolymers,

[0023] - polyolefins,

[0024] - polyesters, and

[0025] - their mixtures.

[0026] A heat sealable packaging material according to this specification can comprise a support layer comprising or consisting of 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, and a grammage of the support layer is preferably in a range between 35 g / m2and 130 g / m2, a barrier-supporting coating layer having a coat weight of 2 to 15 gsm and comprising binding agents at least 20 wt.% of the total dry weight of the barrier-supporting coating layer, wherein

[0027] - a first binding agent of the barrier-supporting coating composition is selected from non-thermoplastic polymers, preferably from starches, hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures, and

[0028] - a second binding agent of the barrier-supporting coating composition is selected from styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, and their mixtures, wherein a ratio of the first binding agent to the second binding agent is preferably from 0.5:1 to 5:1 , more preferably at least 1.1 :1 , a barrier coating layer having a coat weight of 3 to 12 gsm and comprising heat sealable polymer(s) at least 40 wt.% of the total dry weight of the barrier coating layer, wherein the one or more heat sealable polymers are selected from acrylates, ethylene-acrylic acid copolymers, styrene-acrylate copolymers, styrene-butadiene copolymers, polyolefins, polyesters, and their mixtures.

[0029] Surprisingly, the non-thermoplastic binding agent in the barrier-supporting coating improves heat sealability of the barrier coating layer. Surprisingly, the heat sealable packaging material according to this specification has better heat sealability properties than e.g. otherwise similar materials having two barrier coating layers instead of the barrier coating layer on the barrier-supporting coating layer.

[0030] Technical effects of the barrier-supporting coating according to this specification include improved heat sealability as well as improved usability in a packaging machine. Moreover, the heat sealable packaging material according to this specification can be particularly advantageous in a flexible packaging.

[0031] As discussed, the heat sealable packaging material comprises the first precoating layer, which first precoating layer is situated between the paper and the barrier-supporting coating layer. A grammage of the first precoating layer is in a range between 1 gsm and 10 gsm.

[0032] The paper and / or the support layer comprising the precoating layer(s) can be calendered or supercalendered. Technical effect is to provide an improved surface for coatings. Calendering enables lower coat weight of the barriersupporting and the heat sealable coating layer.

[0033] The first binding agent of the barrier-supporting coating layer can be selected from starches, hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures.

[0034] Preferably, the first binding agent is selected from starches, hemicelluloses, polyvinyl alcohols, and their mixtures. More preferably, the first binding agent is selected from starches, hemicelluloses, and their mixtures. Technical effects include introduction of a non-thermoplastic, hydrophilic, water-soluble polymer, and to improve heat sealability of the packaging material when mixed with the second binding agent.

[0035] The first binding agent of the barrier-supporting 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.

[0036] Alternatively, or in addition, the first binding agent of the barrier-supporting 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.

[0037] The second binding agent of the barrier-supporting coating layer is preferably selected from

[0038] - styrene-acrylate copolymers,

[0039] - styrene-butadiene copolymers,

[0040] - acrylates,

[0041] - polyesters, and

[0042] - their mixtures,

[0043] Technical effects of the second binding agent include increasing elasticity of the coating layer and increasing solids content enabling drying of the coating with lower energy use or the option to increase the coat weight at constant drying capacity.

[0044] A ratio of the first binding agent of the barrier-supporting coating layer to the second binding agent of the barrier-supporting coating layer is preferably in a range from 30 to 90, more preferably from 40 to 80. Technical effects include providing improved barrier properties as well as desired film forming, emulsifying and adhesive properties. Technical effects further include improved heat sealability of the barrier coating layer.

[0045] In an advantageous embodiment, the heat sealable polymers are selected from styrene-acrylate copolymers, styrene-butadiene copolymers, polyesters and polyolefins. Most advantageously, the heat sealable polymers are selected from styreneacrylate copolymers and styrene-butadiene copolymers. Thus, most advantageously, the heat sealable polymers consist of, or at least mainly consist of, styrene-acrylate copolymer(s) and / or styrene-butadiene copolymer(s).

[0046] 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.

[0047] In an embodiment, the barrier-supporting coating layer has a mineral pigment content from

[0048] 20 wt.% to 80 wt.%, and / or the barrier coating layer has a mineral pigment content from 0 wt.% to 60 wt.%.

[0049] Technical effects include decreasing manufacturing costs of the product, while obtaining desired barrier properties.

[0050] Preferably, the heat sealable packaging material has a mineral oil barrier (heptane vapour transmission rate) of less than 40 g / m*day, more preferably less than 30 g / m*day, and most preferably less than 20 g / m*day.

[0051] Preferably, the heat sealable packaging material has a WVTR value of less than 150 g / m2*day, determined at 23°C / 85%RH according to standard ISO 2528.

[0052] Preferably, the heat sealable packaging material has a grease barrier over 40 hours, determined according to ASTM F119-82 at 40°C by using chicken fat.

[0053] A package according to this specification can comprise, preferably at least mainly consist of, the heat sealable packaging material according to this specification. The package according to this specification is preferably a flexible package.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] Thanks to the novel heat sealable packaging material, heat sealability of the outermost coating layer can be substantially improved. Further, predetermined barrier properties can be obtained in a more environmentally friendly way than conventionally.

[0058] 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 Cepi Recyclability Test Method Version 2, Oct 7, 2022.

[0059] The solution according to this specification can provide flexible or rigid packaging applications for food, beverages as well as for non-food, where heat sealability and barrier values are needed. Preferably, the heat sealable packaging material is designed to ensure recyclability.

[0060] The packaging material according to this specification is preferably used for packaging food. Effective barriers, include resistance to water vapor, grease, oil, mineral oil, are often required in packaging industry to extend shelf-life of packaged food products.

[0061] Heat sealability is an important property and it has to be assured that tearing of the sealed packaging results in full fiber tear to avoid leakage or unintentional opening of the packaging.

[0062] Advantageously, the heat sealable packaging material is heat sealable at least at 160°C, determined at 0.4-0.8 bar, preferably at 0.6 bar sealing pressure, by using 500 ms dwell time in a laboratory sealing equipment (HSE-3 Laboratory Heat Sealer from RDM Test Equipment). In an embodiment, the heat sealable packaging material is heat sealable at least at 160°C, by using 6 bar operating sealing pressure, by using 500 ms dwell time in a VFFS packaging line.

[0063] Preferably, the heat sealable packaging material is heat sealable at any temperature from 140°C to 160°C, determined at 0.6 bar sealing pressure, by using 700 ms dwell time in a VFFS packaging line.

[0064] Preferably, the heat seal packaging material is heat sealable at as low as possible temperature. The technical effect is energy savings.

[0065] Surprisingly, a sealing temperature of the barrier coating layer can be lowered even when using the same barrier coating layer. The 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. Further, lowering a sealing temperature can result in energy savings.

[0066] Thanks to the novel solution, the barrier coating layer according to this specification can be heat sealable at a 10°C lower temperature compared to the same barrier coating layer without the barrier-supporting coating layer according to this specification.

[0067] Brief description of the drawings

[0068] In the following, the invention will be described in more detail with reference to the appended drawings, in which:

[0069] Figs 1 -3 illustrate examples of heat sealable packaging materials in crosssection,

[0070] Fig. 4 illustrates an example of method steps for manufacturing a heat sealable packaging material,

[0071] Fig. 5a show a SEM image of a packaging material with a precoating layer, and a barrier-supporting coating layer,

[0072] Fig. 5b show a SEM image of a heat sealable packaging material with a precoating layer, a barrier-supporting coating layer, and a barrier coating layer,

[0073] 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

[0074] Figs 7a-b 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.

[0075] Detailed

[0076] In the text, references are made to the figures with the following numerals and denotations:

[0077] 1 heat sealable packaging material,

[0078] 2 support layer,

[0079] 2a paper,

[0080] 3 first precoating layer on a first side of the paper 2a,

[0081] 3a first precoating composition,

[0082] 4 barrier-supporting coating layer,

[0083] 5 barrier coating layer,

[0084] 6 second precoating layer on a second side of the paper 2a,

[0085] 6a second precoating composition,

[0086] 7 barrier-supporting coating composition,

[0087] 8 barrier coating composition,

[0088] 9 precoating unit(s) for precoating(s),

[0089] 10 coating unit for barrier-supporting coating, and

[0090] 11 coating unit for barrier coating.

[0091] Terms and standards

[0092] Unless otherwise indicated, the following standards refer to methods which are used in obtaining stated values of parameters representing quality of the packaging material:

[0093] 1 ) Grammage ISO 536:2019

[0094] 2) Density ISO 534:2011

[0095] 3) Cobbeo and Cobbsoo ISO 535

[0096] 4) WVTR ISO 2528 at 23°C / 50%RH and 23°C / 85%RH

[0097] 5) Grease barrier ASTM F119-82 at 40°C using chicken grease

[0098] 6) Brookfield viscosity SCAN-P 50:84 using RV Brookfield equipment

[0099] 7) Static water retention Modified TAPPI T701 pm-01 using 15 mL coating color, a pressure of 0.4 bar, and a testing time of 30 s. 8) Mineral oil barrier:

[0100] 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.

[0101] 9) Recycling tests determining recyclability are determined according to Cepi Recyclability Test Method Version 2, Oct 7, 2022

[0102] 10) Heat sealability test:

[0103] 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.

[0104] Visual inspection: Seal quality can be manually inspected by using following three criteria:

[0105] Level 1

[0106] There are no fiber tears on the samples, the seam peels apart. The samples have stuck to each other, yet the seam opens, leaving the sample strips with surfaces that remain mostly smooth and glossy. Alternatively, if there is any fiber tear, it is less than 5 mm anywhere along the seam area.

[0107] Level 2

[0108] There are partial fiber tears on the samples, the seam exhibits both fiber tearing and peeling of the barrier coating (or another surface that is being seamed). Alternatively, if initially, there is more than 5 mm of peeling seam at any point across the width of the sample.

[0109] Level 3

[0110] There are fiber tears on the entire surface area of the opened seam. In the center, there may be small (less than 5 mm) patches of barrier coating, or the sample strip may have broken away from the base paper due to fiber tears. Alternatively, if there is less than 5 mm of peeling seam at the start, followed by fiber tears across the entire width of the strip.

[0111] 11 ) Packaging machine testing

[0112] 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).

[0113] 12)The term ‘WVTR’ refers to water vapour transmission rate. The water vapour transmission rate can be determined at 23°C / 50%RH or at 23°C / 85%RH. Unless otherwise indicated, the term WVTR refers to water vapour barrier at conditions of RH 85%, temperature 23°C.

[0114] The term ‘RH’ relates to relative humidity of the air.

[0115] 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.

[0116] The terms ‘gsm’ refers to grams per square meter (g / m2). Unless otherwise indicated, all grammages (e.g., coat weights) are in dry weight.

[0117] 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.

[0118] The embodiments and examples recited in the claims and in the description are mutually freely combinable unless otherwise explicitly stated.

[0119] 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”.

[0120] The term “non-thermoplastic binder” in this application refers to polymeric compounds that perform as a binding agent during the drying of the coating while they do not exhibit a melting point or glass transition.

[0121] In this specification, polymeric binders are included that do not exhibit a melting point or glass transition point below 170 °C and therefore, are not thermoplastic under typical conditions of paper coating equipment using water-based coatings. Non-thermoplastic binders according to this specification include water-soluble polymers such as starch, hemicelluloses other water-soluble or dispersible polysaccharides, polyvinyl alcohol or copolymers of polyvinyl alcohol that form a continuous film during evaporation of water.

[0122] The term "PVA" refers to polyvinyl alcohol. Polyvinyl alcohol is a synthetic polymer, typically prepared by the polymerization of vinyl acetate, followed by a controlled hydrolysis of the ester in the presence of an alkaline catalyst.

[0123] 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.

[0124] The term “flexible package” refers to a package having changeable shape, for example, when filled, or during a use.

[0125] 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.

[0126] 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.

[0127] For the barrier-supporting coating layer, the starch is degraded or converted to obtain solubility and suitable rheological properties. In this specification, the term "starch" particularly refers to starches degraded by chemical, thermal or enzymatic means, which may be referred as dextrin or modified or converted starch.

[0128] 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.

[0129] 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.

[0130] Native starch can be converted also in the laboratory according to the procedure described above.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] The term “coating layer” refers to a thin solid layer that is applied to a surface of a substrate.

[0139] 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.

[0140] 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.

[0141] Support layer

[0142] The support layer 2 comprises a paper 2a having a first side and a second side. Thus, the support layer 2 has a first side and a second side.

[0143] 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 coating layers.

[0144] The support layer comprises a first precoating layer 3 on the paper 2a. Technical effect is to provide improved surface for the paper before applying the barrier coating layers.

[0145] 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.

[0146] 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.

[0147] Preferably, the cellulose-containing natural fibers comprises chemically pulped natural fibre, that is, pulp made in a chemical pulping process. In an advantageous example, the content of chemically pulped natural fibres in all the cellulose-containing natural fibers used in the 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.

[0148] Preferably, the paper 2a does not contain so-called mechanical pulp.

[0149] Preferably, the paper does not contain highly refined fibers having a Schopper- Riegler (SR) value of above 70, or above 90 or even above 92 as determined by standard ISO 5267.

[0150] Advantageously, the heat sealable packaging material is nanocellulose free.

[0151] 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.

[0152] Preferably, the paper 2a does not contain viscose fibers. Thus, the paper is preferably viscose free paper. Thus, advantageously, the heat sealable packaging material is free of viscose. Technical effect is to improve environmental friendliness of the product. Furthermore, preferably, the paper does not contain synthetic fibres or filaments. Advantageously, the heat sealable packaging material is free of synthetic fibres and filaments.

[0153] The paper 2a refers to an uncoated structure, i.e., an uncoated paper. In an embodiment, the support layer 2 is an uncoated paper.

[0154] As discussed, the support layer 2 has, in addition to the paper 2a, at least the first precoating layer 3 and, optionally, the second pre coating layer 6. Thus, the paper 2a can be coated with precoating composition(s) 3a, 6a.

[0155] The support layer 2 has the first precoating layer 3 on the first side of the paper 2a and, optionally, a second precoating layer 6 on the second side of the paper 2a.

[0156] If the support layer 2 comprises both; the first precoating layer 3 and the second precoating layer 6, the coating compositions of the first and second precoating layers preferably differ from each other.

[0157] Each precoating layer 3, 6 can have a grammage in a range between 0.3 gsm and 10 gsm. Preferably, each precoating layer 3, 6 has a grammage from 0.4 to 8 gsm, more preferably from 0.5 to 7 gsm, and most preferably from 0.6 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 of the first precoating layer is to prepare the surface of the support layer for the barrier-supporting coating composition and to work as an adhesion promoter to the barrier-supporting coating layer.

[0158] Thickness of the first precoating layer 3 is preferably between 0.5 to 10 pm, and more preferably between 0.7 pm and 8 pm, and most preferably from 1 to 5 pm. Technical effect is to prepare the surface of the support layer 2 for barrier coatings cost efficiently.

[0159] Thickness of the second precoating layer 6, if used, is preferably between 0.3 to 7 pm, and more preferably between 0.4 pm and 5 pm, and most preferably from 0.5 to 3 pm. Technical effect is to decrease dusting tendency of the heat sealable packaging material. Another technical effect is to prepare the surface of the support layer 2 for a printing cost efficiently.

[0160] The first precoating layer 3 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%, more preferably 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).

[0161] The second precoating layer 6 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%, more preferably in a range between 35% and 100%, and most preferably in a range between 35% and 100%, referring to relative proportion of the binding agent(s) in the total content of the precoating(s).

[0162] The binding agent(s) of the first and / or second precoating layer(s) 3, 6 can be selected from a group comprising or consisting of: starch, modified starch, enzymatically converted starch, polyvinyl alcohol, ethylene vinyl alcohol, modified cellulose, dispersions of different polyesters such as PLA, PBS, PBAT, PHAs.

[0163] Advantageously, the binding agents of the first and / or second precoating layer(s) 3, 6 comprise 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.

[0164] In an embodiment, the binding agent(s) of the first precoating layer 3 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.

[0165] The precoating layer 3, 6 can further contain pigments. The precoating layer 3, 6 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.

[0166] The first precoating layer 3 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. The second precoating layer 6 can comprise mineral pigments in a range between 0 wt.% and 75 wt.%, preferably in a range between 0 wt.% and 70 wt.%, and more preferably in a range between 0 wt.% and 68 wt.%, calculated from the total dry weight of the precoating layer 6. 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, even omitted.

[0167] Preferably, the binding agent(s) of the second precoating layer 6 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 6 is to prevent dusting of the heat sealable packaging material. As discussed, the second precoating layer 6 can contain pigments. Technical effect of pigments is to provide improved surface for printing.

[0168] As discussed, the support layer 2 comprises the first precoating layer 3 on the first side of the paper 2. Optionally, the support layer 2 can comprise the second precoating layer 6 on the second side of the paper 2a. Thus, the first side of the paper 2a can be coated with a first precoating composition 3a for obtaining the first precoating layer 3. The second side of the paper 2a can be coated with a second precoating composition 6a for obtaining the second precoating layer 6.

[0169] Preferably, the support layer 2 comprises only one precoating layer 3, 6 on one or both sides of the paper 2a.

[0170] Grammage of the support layer 2 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 2 may be, for example, in a range between 40 gsm and 120 gsm. In an advantageous example, the grammage of the support layer 2 is between 45 gsm and 110 gsm. Technical effect is to obtain heat sealable packaging material having good strength properties. Support layer 2 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 2 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.

[0171] In an embodiment, density of the support layer 2 is less than 1000 kg / m3, more preferably in a range between 800 kg / m3and 990 kg / m3, still more preferably in a range between 820 kg / m3and 970 kg / m3, and most preferably equal to or less than 950 kg / m3, such as in a range between 850 kg / m3and 940 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.

[0172] In another embodiment, density of the support layer is at least 1000 kg / m3, such as in a range between 1000 kg / m3and 1200 kg / m3, more preferably in a range between 1020 kg / m3and 1170 kg / m3, and most preferably in a range between 1050 kg / m3and 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.

[0173] Due to the barrier-supporting and the barrier coating layers, support layer 2 does not need to provide low water vapour transmission rate. In an embodiment, WVTR (23°C / 85%RH, ISO 2528) of the support layer 2 is higher than 500 g / m2*day. Technical effect includes improved easiness of the manufacturing process as the support layer 2 (as such) does not need to provide water vapour barrier.

[0174] Furthermore, preferably, mineral oil barrier (HVTR method, Heptane vapour transmission rate) of the support layer 2 is higher than 100 g / m2*day. Technical effect includes further improved easiness of the manufacturing process as the support layer 2 (as such) does not need to provide mineral oil barrier.

[0175] Grease barrier (ASTM F119-82, 40°C, chicken fat) of the support layer 2 can be less than 2 hours, or even less than 1 hour. Technical effect includes improved easiness of the manufacturing process as support layer 2 (at least as such) does not need to provide grease barrier.

[0176] Barrier-supporting coating layer

[0177] The heat sealable packaging material 1 comprises the barrier-supporting coating layer 4. The barrier-supporting coating composition 7 contains two or more binding agents. Thus, the barrier-supporting coating layer contains a first binding agent and a second binding agent.

[0178] The barrier-supporting coating layer 4 can have binding agent content of at least 20 wt.%, such as in a range between 20% and 80%, preferably at least 22%, such as in a range between 22% and 75%, and most preferably in a range between 25% and 70%, referring to relative proportion of binding agents in the total content of the barrier-supporting coating layer (by dry weight).

[0179] Total content of said first and second binding agents is preferably at least 80%, more preferably at least 90%, and most preferably at least 95% and up to 100%, determined from total dry weight of all binding agents in the barriersupporting coating layer.

[0180] The first binding agent can be selected from non-thermoplastic polymers, preferably from starches, hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures.

[0181] The main technical effect of the non-thermoplastic binder in the barriersupporting coating layer 4 is to improve heat sealability of the heat healable packaging material. Another technical effect is to prepare the foundation for barrier properties, such as for water vapor and grease barrier properties.

[0182] The first binding agent of the barrier-supporting coating composition can comprise or consist of hemicellulose(s) and / or starch(es). The first binding agent can include at least one of a water-soluble hemicellulose and a water- soluble starch.

[0183] Thus, the binding agents of the barrier-supporting coating composition can 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 barrier-supporting coating composition.

[0184] In an embodiment, the first binding agent of the barrier-supporting 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.

[0185] In an embodiment, the first binding agent of the barrier-supporting 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.

[0186] In an embodiment, the first binding agent of the barrier-supporting 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 crosslinked 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.

[0187] Preferably, the first binding agent of the barrier-supporting coating layer contains or consists of at least one of modified starch and enzymatically converted starch.

[0188] In an embodiment, the first binding agent of the barrier-supporting 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.

[0189] 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.

[0190] 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.

[0191] 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 %.

[0192] The starch material may be from any source including, for example, wheat, tapioca, potato, rice, barley, corn, or pea.

[0193] The starch(es), if used in the barrier-supporting coating composition, 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 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.

[0194] The hemicellulose(s), if used in the barrier-supporting 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.

[0195] In a preferred embodiment, the starch is a low molecular weight starch material having a weight average molecular weight (Mw) from 15 000 to 500000 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 barrier-supporting 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 42 weight-% while maximizing the grease barrier of the coating layer.

[0196] The binding agents of the barrier-supporting 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 60 wt.% and less than 80 wt.% of starches or hemicelluloses. Technical effects include improved cost efficiency and runnability. 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.

[0197] In addition to said polysaccharides, or alternatively, the first binding agent can be selected from polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures. Technical effect is to provide odorless, and non-toxic material having improved film forming properties, particularly suitable for foodstuff packaging. Another technical effect is the inherent biodegradability.

[0198] Thus, the barrier-supporting coating layer 4 can contain a first binding agent selected from

[0199] - hemicelluloses, - starches,

[0200] - polyvinyl alcohols,

[0201] - ethylene-vinyl alcohol copolymers, and

[0202] - their mixtures.

[0203] Technical effect of is to provide lower sealing temperature compared to other kinds of barrier-supporting layers that are free of the first binding agent. Another technical effect is enabling sealing of packaging that has not been sealable to full fiber tear at any temperature below 200°C. Still, another technical effect is to create desired grease barrier. Still another technical effect is to provide odorless, and non-toxic material having improved film forming properties suitable e.g. for foodstuff packaging.

[0204] 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 13 to 35 weight-%, determined of total amount of binding agents. Technical effects include improved film formation properties.

[0205] 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.

[0206] The binding agents of the barrier-supporting 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 13 wt.% to 35 wt.% of polyvinyl alcohol. Technical effect is to increase the elasticity of the coating layer.

[0207] 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.

[0208] The second binding agent can be selected from latexes. Preferably, the second binding agent comprises 10 to 60 wt.% of latex of the total dry weight of the binding agents. Latex 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 styrene-butadiene latex or styrene-acrylate latex, can be produced on a large scale and its cost is typically lower. The second binding agent of the barrier-supporting coating layer is selected from styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, polyesters, and their mixtures.

[0209] Advantageously, the second binding agent is selected from styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, and their mixtures, preferably comprising said polymer(s) a total amount of 10 to 60 wt.% of the total dry weight of the binding agents.

[0210] Most preferably, the second binding agent is selected from styrene-acrylate copolymers, styrene-butadiene copolymers, and their mixtures, preferably comprising said polymer(s) a total amount of 10 to 60 wt.% of the total dry weight of the binding agents.

[0211] Preferably, the second binding agent has 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 as tackiness during the manufacturing process can be avoided.

[0212] The binding agents of the barrier-supporting coating layer 4 can comprise at least 10 wt.%, preferably from 10 wt.% to 60 wt.%, more preferably at least 18 wt.% and less than 55 wt.%, and most preferably at least 20 wt.% and less than 50 wt.% polymers selected from styrene-acrylate polymers, styrene- butadiene copolymers, acrylates, and their mixtures. Technical effects are introduction of elasticity to the packaging material.

[0213] Thus, as discussed, the barrier-supporting coating layer 4 preferably contains

[0214] - a first binding agent preferably selected from modified starches, enzymatically converted starches, hemicelluloses, polyvinyl alcohols, and their mixtures, and

[0215] - a second binding agent preferably selected from styrene-acrylate polymers, styrene-butadiene copolymers, acrylates, and their mixtures.

[0216] Technical effect is to improve the heat sealability of the barrier coating layer by using a mixture of said two binding agents. The presence of the first binding agent improves the heat sealability compared to using exclusively the second 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.

[0217] Preferably, hemicellulose(s), starch(es) and latex(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 barrier-supporting coating. Technical effect is the improved heat sealability and good basis for grease barrier and possibility to tailor the viscosity of the coating color.

[0218] Most advantageously, starch(es) and latex(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 barriersupporting coating. Technical effect is to utilize the beneficial properties of both binding agents.

[0219] Preferably, the first binding agent of the barrier-supporting coating layer 4 is 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 .

[0220] Ratio of the first binding agent to the second binding agent is preferably in a range from 0.5:1 to 5:1 , more preferably from 0.6:1 to 4:1 , still more preferably from 0.8:1 to 3:1 , and most preferably from 0.9:1 to 2.5:1. Technical effects include improved heat sealability. Technical effects further include providing improved barrier properties as well as excellent film forming, emulsifying and adhesive properties.

[0221] In an embodiment, ratio of the first binding agent to the second binding agent is 1 :0.67 to 4:1 , or from 1 :0.7 to 3:1. Technical effects include particularly improved heat sealability.

[0222] In an advantageous embodiment,

[0223] - the first binding agent of the barrier-supporting coating composition is selected from non-thermoplastic polymers, preferably from starches, hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures, most preferably the first binding agent comprises or consists of starch(es), and - the second binding agent of the barrier-supporting coating composition is selected from styrene-acrylate copolymers, styrene-butadiene copolymers, and their mixtures, wherein ratio of the first binding agent to the second binding agent is preferably from 0.6:1 to 5:1 , more preferably from 0.8:1 to 4:1 , still more preferably at least 1.1 :1 such as from 1.1 :1 to 3:1 , still more preferably at least 1.1 :1 , such as from 1.2:1 to 2.5:1 , and most preferably at least 1.5:1. Technical effects include improved heat sealability. Technical effects further include providing improved barrier properties together with excellent film forming, emulsifying and adhesive properties.

[0224] Most preferably, for obtaining particularly improved properties for the packaging material, the ratio of the first binding agent to the second binding agent is at least 1.1 :1 , more preferably at least 1.2:1 , still more preferably at least 1.3:1 , or at least 1.4:1 , and most preferably at least 1.5:1. A further technical effect is to modify the properties of the barrier-supporting layer for the next coating layer.

[0225] One technical effect of higher starch content is to provide higher biobased and biodegradable content for the heat sealable packaging material, and one technical effect of higher PVA content is to provide higher biodegradable content. Furthermore, both, starch and PVA, modify the properties of the barrier-supporting layer for the next coating layer. Further, one technical effect of higher latex content is to maximize solids content to a suitable solids content range.

[0226] Advantageously, solids content of the barrier-supporting coating composition 7 is from 45 to 62 wt.%, more preferably 47-58 wt.%, still more preferably 48- 56 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.

[0227] The barrier-supporting 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.

[0228] The barrier-supporting coating layer 4 can comprise mineral pigments in a range between 20 wt.% and 80 wt.%, preferably in a range between 25 wt.% and 77 wt.%, and more preferably in a range between 30 wt.% and 75 wt.%, calculated from the total dry weight of the barrier-supporting 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. It also enables higher solids content and decrease the energy need for evaporation.

[0229] Preferably, the main pigment of the barrier-supporting 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 2 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.

[0230] The barrier-supporting coating composition and the barrier-supporting coating layer preferably comprises the binding agents and the mineral pigments in a dry weight ratio from 0.2:1 to 6:1 , more preferably from 0.25:1 to 4:1 , and most preferably from 0.3:1 to 3:1. Technical effect is tailoring the rheological properties and decreasing the costs of chemicals.

[0231] The barrier-supporting coating composition and the barrier-supporting 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 barrier-supporting coating layer.

[0232] The barrier-supporting coating composition 7 and, hence, the barriersupporting 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.

[0233] Grammage of the barrier-supporting coating layer is preferably 2 to 15 gsm, more preferably 3 to 13 gsm, and most preferably 4.5 to 10.0 gsm (by dry weight). Technical effect is to provide improved barrier properties for the heat sealable packaging material cost-efficiently.

[0234] A thickness of the barrier-supporting coating layer 4 can be in average in a range between 1 .5 pm and 13 pm, preferably between 2.6 to 11 pm, and more preferably between 4 pm and 10 pm, and most preferably from 4.5 to 9.5 pm. Technical effect is to obtain protection from grease cost efficiently with the barrier-supporting coating. Another technical effect is that barrier-supporting coating layer 4 and the barrier coating layer create a synergistic effect providing barrier properties for the heat sealable packaging material. The barrier-supporting coating composition 7 can have a Brookfield viscosity of 200-2000 mPas, preferably 300-1900 mPas, more preferably 400-1800 mPas when measured at 40°C, 100 rpm, at solids contents of 45-60%. Technical effect is that the viscosity is suitable for pumping coating color to the storage tank and the coating units.

[0235] Barrier coating layer

[0236] The heat sealable packaging material 1 comprises a barrier coating layer 5.

[0237] One technical effect of the barrier coating layer 5 is to provide heat sealability for the heat sealable packaging material 1. Another technical effect is to provide improved water vapor barrier properties. Still another technical effect of the barrier coating layer according to this specification is providing medium grease barrier of the heat sealable packaging material by filling possible pinholes. Another technical effect is to provide medium water vapor barrier at conditions of elevated humidity, such as 23°C and 85% humidity. Yet another technical effect of the 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.

[0238] The support layer 2 can be coated with a barrier-supporting coating composition 7 and a barrier coating composition 8 to obtain the heat sealable packaging material 1 comprising the barrier-supporting coating layer 4, and the barrier coating layer 5.

[0239] Preferably, the heat sealable packaging material 1 comprises the first precoating layer 3, the barrier-supporting coating layer 4, and the barrier coating layer 5 on the same side of the paper 2a. Preferably, the barriersupporting coating layer 4 is on the first precoating layer 3 and the barrier coating layer 5 is on the barrier-supporting coating layer 4. The barriersupporting coating layer 4 can be directly on the first precoating layer 3 and the barrier coating layer 5 can be directly on the barrier-supporting coating layer 4. The technical effect is to obtain improved heat sealability as well as improved barrier properties for the heat sealable packaging material.

[0240] The barrier coating layer 5 can comprise one or more heat sealable polymers. Preferably, the barrier coating layer 5 comprises 40 to 100 wt.% of heat sealable polymer(s) of the total dry weight of the barrier coating layer 5. Technical effect is to provide heat sealability together with improved barrier properties. The barrier coating layer 5 can comprise at least one latex and / or another polymer dispersion-based barrier coating that shows heat sealable properties.

[0241] Preferably, the barrier coating composition 8 is based on latex. Preferably, the barrier coating layer 5 comprises 65 to 100 wt.% of latex of the total dry weight of the barrier coating layer 5. Technical effect is to provide improved barrier properties as well as excellent runnability and high-solid content capacity.

[0242] 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.

[0243] Ethylene-acrylic acid copolymer(s) (EAAs), if used, can be produced by reacting ethylene with acrylic acid. Technical effects of EAA include that water resistance, flexibility, and chemical resistance are introduced by the ethylene segments, while the acrylic acid units provide polarity, adhesion, low temperature heat sealability, hot tack strength and toughness. EAAs have superior heat seal properties.

[0244] In an embodiment, the polymer dispersion of the barrier coating layer 5 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.

[0245] Polyesters, if used, can be poly(butylene succinate) (PBS) or its copolyesters such as poly(butylene succinate-co- adipate) (PBSA), poly(butylene adipate- co-terephthalate) (PBAT), poly(lactic acid) (PLA), poly(caprolactone) (PCL) such as poly(£-caprolactone) or its copolyesters, or poly(hydroxy alkanoate) (PHA) such as poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV), poly(3- hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), or mixtures thereof.

[0246] 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 grease and water vapor barrier properties and heat sealability for the heat sealable packaging material.

[0247] 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 ethylene-acrylic acid copolymer(s), polyolefins.

[0248] Technical effects include providing water vapor barrier, improving grease barrier, and providing heat sealability for the heat sealable packaging material.

[0249] 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 ethylene-acrylic acid copolymer(s),

[0250] Technical effects include providing water vapor barrier, improving grease barrier, and providing heat sealability for the heat sealable packaging material.

[0251] 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).

[0252] Technical effects include providing improved water vapor barrier, grease barrier, and heat sealability for the heat sealable packaging material, without e.g. polyolefins.

[0253] Thus, the 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.

[0254] The (dispersed) heat sealable polymers 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.

[0255] The barrier coating layer can comprise 3 to 35 wt.%, preferably 5 to 30 wt. %, and most preferably from 10 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.

[0256] 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.

[0257] The term “soy wax” refers to natural wax derived from soybeans.

[0258] 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.

[0259] Technical effect of said waxes is to maintain the desired properties while increasing the biobased content.

[0260] The barrier coating composition and hence the 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 barrier coating layer.

[0261] Furthermore, the barrier coating composition 8 can contain solid, insoluble pigments, providing e.g., opacity or color, such as talc, calcium carbonate, and / or titanium dioxide.

[0262] In an embodiment, the 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.

[0263] The barrier coating layer 5 can comprise mineral pigments 0 to 60 wt.%, preferably 10 to 40 wt.%, more preferably 15 to 30 wt.%, and most preferably equal to or less than 25 wt.%, calculated from the total dry weight of the 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 barrier coating layer with said pigment addition to the selected polymer materials shows suitable heat sealability properties for the use in packaging lines. However, in an embodiment, the barrier coating layer is free of mineral pigments.

[0264] The 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.

[0265] In a preferred embodiment, the barrier coating layer comprises talc.

[0266] In a preferred embodiment, the barrier coating layer comprises kaolin. Advantageously, barrier coating layer 5 comprises kaolin 0 to 60 wt.%, preferably 10 to 40 wt.%, more preferably 15 to 30 wt.%, and most preferably equal to or less than 25 wt.%, calculated from all mineral pigments in the barrier coating layer 5. Kaolin can be easily dispersed into water, improving easiness of the manufacturing process while providing advantages of platy pigments. However, in an embodiment, the barrier coating layer is free of mineral pigments, including kaolin.

[0267] In one preferred embodiment, the barrier coating layer comprises calcium carbonate. Advantageously, barrier coating layer 5 comprises calcium carbonate 0 to 60 wt.%, preferably 10 to 40 wt.%, more preferably 15 to 30 wt.%, and most preferably equal to or less than 25 wt.%, calculated from all mineral pigments in the barrier coating layer 5. Technical effects include improved rheological properties and decreased costs, while maintaining suitable heat sealability properties for the use in packaging lines.

[0268] Grammage of the barrier coating layer is preferably 3 to 12 gsm, more preferably 3.5 to 9 gsm, and most preferably 4 to 7 gsm (by dry weight). Technical effect is to provide improved heat sealability and barrier properties for the heat sealable packaging material cost-efficiently. A thickness of the barrier coating layer 5 can be in average in a range between 1.5 pm and 13 pm, preferably between 2 pm and 10 pm, more preferably between 3 pm and 8 pm, and most preferably from 3.5 to 7 pm. Technical effect is to obtain good level of grease and water vapor resistance cost efficiently with the barrier coating.

[0269] Total amount of heat sealable polymers in the barrier coating layer 5 can be at least 40 wt.%, such as 40 to 100 wt.%, preferably 60 to 100 wt.%, and most preferably from 70 to 100 wt.%, calculated from the total dry weight of the barrier coating layer 5. Technical effects include improved barrier properties and heat sealability.

[0270] The barrier coating layer 5 preferably forms the topmost coating layer on the first side of the heat sealable packaging material.

[0271] Heat sealable packaging material

[0272] As discussed, the heat sealable packaging material has the support layer 2, the barrier-supporting coating layer 4, and the barrier coating layer 5.

[0273] Preferably, the barrier-supporting coating layer 4 is situated between the support layer 2 and the barrier coating layer 5, and the barrier coating layer 5 is on top of the barrier-supporting coating layer 4.

[0274] The heat sealable packaging material can have at least one side, and preferably only one side, that comprises the barrier-supporting coating layer 4 and the barrier coating layer 5. Preferably, the heat sealable packaging material has the said coatings 4, 5 only on the first side of the support layer 2. Technical effect is to decrease environmental load, such as the carbon dioxide load, and to provide cost efficiently environmentally friendly heat sealable barrier material.

[0275] The other side of the heat sealable packaging material may only have, for example, the second precoating layer 6. However, it is also possible that the barrier-supporting coating layer 4 and / or the barrier coating layer 5 are provided on both sides of the support layer 2.

[0276] Thus, the heat sealable packaging material may have the second precoating layer. The second precoating layer 6 can be a surface size layer. The second precoating layer 6 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 only, or the second side of the paper can comprise the second precoating layer. In an embodiment, the second side of the paper comprises two coating layers, wherein another coating layer is on the second precoating layer for further improving printability of the heat sealable packaging material.

[0277] The heat sealable packaging material can have at least one side designed for printing. Preferably, the second side of the heat sealable packaging material is designed for printing, i.e., the second side of the heat sealable packaging material is printable.

[0278] The printable side(s) is / are preferably printable by using at least one of

[0279] » digital printing, such as digital inkjet printing,

[0280] « flexography,

[0281] ® rotogravure, and

[0282] • offset lithography.

[0283] Thus, preferably, the heat sealable packaging material is a printable heat sealable packaging material. Technical effect is to improve easiness of printing process for packages comprising the heat sealable packaging material.

[0284] In an advantageous embodiment, the heat sealable packaging material comprises the barrier supporting and 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 is preferably configured to be printable as such. Alternatively, the second precoating 6 can be configured to be overprinted with a pigment coating, and a printing. Alternatively, the heat sealable packaging material can comprise an additional coating layer on top of the second precoating layer, wherein the additional coating layer is designed for printing. Technical effect is that the barrier layers can provide suitable heat sealability and 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.

[0285] If the heat sealable packaging material comprises the second precoating layer and an additional coating layer on the second precoating layer, the additional coating layer can comprise

[0286] - one or more pigments, and

[0287] - one or more binders selected from styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, and their mixtures, wherein a ratio of pigments to binders is preferably 100:7 to 100:15, more preferably 100:8 to 100:12, and still more preferably 100:9 to 100:11. The technical effect is to improve printability of the heat sealable packaging material.

[0288] If the heat sealable packaging material comprises the second precoating layer and the additional coating layer on the second precoating layer, the additional coating layer can have a coat weight from 1 gsm to 18 gsm, preferably in a range between 3 gsm and 15 gsm, and most preferably in a range between 5 gsm and 13 gsm. The technical effect is to improve printability of the heat sealable packaging material.

[0289] The heat sealable packaging material can have the support layer 2 comprising the paper 2a and the first precoating layer, the barrier-supporting coating layer 4 comprising a first binding agent, preferably selected from starches, hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures, and a second binding agent selected from styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, polyesters, and their mixtures, and the barrier coating layer 5 comprising dispersible heat sealable polymer selected from acrylates, ethylene-acrylic acid copolymers, styreneacrylate copolymers, styrene-butadiene copolymers, polyolefins, polyesters, and their mixtures.

[0290] A technical effect is to provide environmentally friendly heat sealable packaging material having improved heat sealability and good barrier properties.

[0291] Thus, the heat sealable packaging material comprises the barrier-supporting layer and the barrier layer, wherein the barrier-supporting layer can provide improved foundation for heat sealability and barrier properties so that when combined with the barrier layer, the heat sealable packaging material can provide improved heat sealability as well as desired barrier properties for grease and water vapor.

[0292] 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.

[0293] The heat sealable packaging material is typically suitable for recycling in a fiber stream according to CEPI recyclability laboratory test method, Version 2, October 2022. 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.

[0294] It is of advantage to use starch as the first binding agent, because starch is a biobased binder. The technical advantage is reduction of fossil-based material.

[0295] 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, and modified starches 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.

[0296] 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.

[0297] 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.

[0298] Furthermore, particularly if a starch at high consistency is used as the first binding agent for the barrier-supporting coating layer 4 (instead of e.g. polyvinyl alcohol) together with the 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.

[0299] The heat sealable packaging material can have a WVTR value of less than 150 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 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.

[0300] The heat sealable packaging material can have a grease barrier over 40 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 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.

[0301] Heat sealability can be determined at 0.6 bar sealing pressure (i.e., jaw pressure), by using 500 ms dwell time. Thus, the heat sealable packaging material is preferably heat sealable at 160°C by using jaw pressure of 0.6 bar and dwell time of 500 ms.

[0302] The heat sealable packaging material according to this specification is preferably heat sealable at 160°C, preferably at least from 140°C to 160°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. Low sealing times for achieving heat sealability can enhance process efficiency in packaging.

[0303] Furthermore, the heat sealable packaging material is preferably heat sealable at 160°C or lower, preferably at least from 140°C to 160 °C, by using any jaw pressure from 0.2 bar to 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.

[0304] As discussed, 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, and the seal quality can be manually inspected as described in this specification.

[0305] In an embodiment, the heat sealable packaging material 1 at least essentially consist of the support layer, the barrier-supporting coating layer, and the barrier coating layer, and optionally there may be a printing on the second side of the heat sealable packaging material.

[0306] In a preferred embodiment, the heat sealable packaging material has the first precoating, barrier-supporting coating layer, and the barrier coating layer on the first side of the support layer, and the second precoating layer 6, preferably designed for printing, on the second side of the paper 2a.

[0307] Thanks to the heat sealable packaging material, oxygen, mineral oil, and water vapor barrier can be improved, compared to conventional environmentally friendly heat sealable materials. Further, the heat sealable packaging material typically has good sealability so that good barrier properties can be provided over the sealing cost efficiently.

[0308] Manufacturing method

[0309] A method for manufacturing a heat sealable packaging material can comprise the following steps: supplying a support layer 2 comprising a paper 2a and a first precoating layer 3, applying a barrier-supporting coating composition 7 onto the support layer 2 in a form of an aqueous dispersion, thereby forming a barriersupporting coating layer 4, and applying a barrier coating composition 8 onto the barrier-supporting coating layer 4 in a form of an aqueous dispersion, thereby forming a barrier coating layer 5.

[0310] The support layer 2 can be made by a paper machine.

[0311] The paper 2a is suitably coated by a precoating unit 9 for applying the precoating composition(s) 3a, 6a. The precoating unit 9 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.

[0312] The barrier-supporting coating composition 7 can be applied onto the support layer 2 by a barrier-supporting coating unit 10 for applying the barriersupporting coating composition 7. The barrier-supporting coating composition 7 can be applied in the form of an aqueous composition. The barrier-supporting 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.

[0313] The barrier coating composition 8 can be applied by a barrier coating unit 11 for applying the barrier coating. The barrier coating composition 8 can be applied in the form of an aqueous composition. The 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.

[0314] Package

[0315] Packages can be produced from the heat sealable packaging material.

[0316] 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.%, preferably at least 70 wt.% (by dry weight) of a package.

[0317] A package can comprise the heat sealable material, for example, in a laminate structure with another paper or film, or other papers or films.

[0318] Thus, in an embodiment, the heat sealable packaging material is used in a packaging laminate construction.

[0319] The package can be a flexible package. Flexible packages include a flow pack for ice cream or candy bars, pillow and gusset for confectionary and cereal, stand-up for coffee and dishwasher tablets, and sachets and poches for spices and dried soups.

[0320] 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.

[0321] Person skilled in the art fully understands that several different packaging formats can be produced with these packaging machinery types.

[0322] Experimental tests

[0323] Example 1

[0324] Starch samples were prepared by conventional cooking of a modified starch.

[0325] Table 1. Viscosity of a representative cooked starch sample at announced solids content and temperature.

[0326] Example 2

[0327] Pilot test coating trials were performed on a paper substrate with a precoating comprising a binder and a platy pigment.

[0328] Coating compositions were prepared in batch mixers for pilot trials. The coating compositions properties for the barrier-supporting coating layer are shown in Table 2. A barrier-supporting layer according to this specification was applied on to a first precoating layer in a pilot coating facility according to this specification. Properties of the obtained product were determined. The results are shown in Table 2.

[0329] Table 2. Coating composition descriptions and properties as well as barrier properties of paper with first precoating and barrier-supporting coating.

[0330] 1Water absorption measured as Cobb 60s value at 50% relative humidity and

[0331] 23°C, standard ISO 535

[0332] 2Water vapor transmission rate at 50% or 85% relative humidity and 23°C, standard ISO 2528

[0333] 3Grease resistance at 40°C using chicken grease, standard ASTM F119-82

[0334] 4KIT value5Heptane transmission rate at 50%relative humidity and 23°C, according to method described above

[0335] The solids contents of starch-containing coating compositions were all at least 49% and resulting in a Brookfield viscosity range (100 rpm) of 830-1830 mPas measured at temperatures of 29-36°C in most cases. There is still room for using higher solids content as higher coating color temperatures are possible in mill coaters and higher temperature results in lower temperature for a specific coating color. All listed coating compositions were suitable for blade coating in the pilot coating machine.

[0336] The first coating functions as barrier-supporting layer. For the trial points with the precoated substrate coated with the barrier-supporting layer only, the water vapor barrier at elevated humidity remains rather high (> 700 g / m2*d) and the KIT values remain moderate with maximum value of 5-9.

[0337] In addition, with the structure with precoating and barrier-supporting coating on the paper, no heat seal properties are obtained.

[0338] Example 3

[0339] Samples from the trial points were overcoated in pilot scale using a coating composition comprising a latex, natural-based wax, and optionally a pigment.

[0340] Coating compositions were prepared in batch mixers for pilot trials. The coating compositions properties for the 2. coatings (barrier layer) are shown in Table 3. Different barrier coating layers according to this specification were applied in a pilot coating facility on to the barrier-supporting layers of the example 2. The test points were as follows:

[0341] Table 3. Coating composition descriptions and properties as well as barrier properties of paper with first precoating, barrier-supporting coating, and barrier coating.

[0342] 1Water absorption measured as Cobb 60s and Cobb 300s values at 50% relative humidity and 23°C, standard ISO 535

[0343] 2Water vapor transmission rate at 50% or 85% relative humidity and 23°C, standard ISO 2528

[0344] 3Grease resistance at 40°C using chicken grease, standard ASTM F119-82

[0345] 4Heptane transmission rate at 50%relative humidity and 23°C, according to method described above

[0346] The paper coated with precoating, barrier-supporting coating and barrier coating shows further improved barrier properties against grease reaching values of > 40h. All samples showed an excellent mineral oil barrier measured as heptane vapor transmission rate (HVTR).

[0347] The water vapor barrier performance at 85% humidity was significantly improved by the barrier coating reaching values below 150 (g / m2d). The barrier coating also introduced heat sealability.

[0348] The values were obtained for up to 80% starch as binder in barrier-supporting coating and even with pigment content of 71 % in barrier-supporting coating.

[0349] Example 4

[0350] The materials of example 3 were tested for heat sealability (paper samples with first precoating, barrier-supporting coating, and barrier coating). The maximum force at tear and adhesive is shown in Table 4. Table 4. Heat sealability of heat sealable packaging material (paper with precoating, barrier-supporting coating and barrier coating).

[0351] The heat sealability of the heat sealable packaging material is on an excellent level with high seal strength and good adhesion for samples with 50% or more starch in the barrier-supporting layer. These sealed samples showed full fiber tear in visual evaluation of the sealing area at pressure levels of 0.2-1 .6 bar with a sealing time of 0.5 s at 160 °C. The samples without starch in the barriersupporting layer did not achieve full fiber tear (visual evaluation level 2) at any pressure level. This shows superior sealing behaviour of the samples with 50% starch or more in the barrier-supporting layer. Fig. 6 shows the strength-strain curve for sample #B003 for all reported pressures including parallel measurements.

[0352] Example 5

[0353] Papers coated with varying pigment content were tested for heat sealability of the heat sealable barrier coating. The coating composition, maximum force at tear and adhesive is shown in Table 5.

[0354] Table 5. Test specimen of coated paper (15 mm wide) with shown composition were tested for seal quality and seal strength according to ASTM F2029-16

[0355] 1PO-disp. = polyolefin dispersion

[0356] The examples show that heat sealable coatings can be achieved with pigment content of up to 60%. The technical advantages of using high pigment loadings include reduction of cost and good runnability in a typical blade coater.

[0357] Example 6

[0358] The recyclability of the heat sealable packaging material (with precoating, barrier-supporting coating, and barrier coating from Example 3) was tested according to Cepi Recyclability Test Method Version 2, Oct 7, 2022. The testing results are compiled in Table 6.

[0359] Table 6. Recycling test results for the heat sealable packaging material. Trial

[0360] The recyclability of the reference sample - comprising the highest amount of latex in the barrier-supporting layer - was excellent (score 99) with excellent yield level of 99%, no visual impurities and minor sheet adhesion. This indicates that also the other samples that contain starch as 1. binder in the barrier-supporting layer would show excellent performance in recyclability tests. The technical advantage is that the packaging materials according to Example 3 are recyclable in a standard recycling mill. Example 7 Packaging trials with the heat sealable packaging material (with the first precoating, barrier-supporting coating, and barrier coating from Example 3) was performed with a commercial vertical-form-fill-seal (VFFS) machine without any machinery modifications.

[0361] The operating window for the VFFS machine was determined based on the results obtained from laboratory heat-seal tests (Example 4).

[0362] 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.

[0363] 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-b. Fully colored areas with black in Figures 7a and 7b denote the typical operating window of a sample with 50% or more starch in the barriersupporting layer.

[0364] In Table 7, seal temperatures of packaging trials at convenient sealing times for top / bottom and longitudinal seals are shown for the tested materials.

[0365] Table 7. Minimum seal temperatures for heat sealable packaging material (paper with precoating, barrier-supporting coating and barrier coating) according to Example 3.

[0366] * operating pressure

[0367] 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 introduction of 50% starch to the binder of the barriersupporting layer decreased the seal temperature by minimum of 10 degrees according to #A022 compared to #A16 and #A028. In the case of the B series, introduction of 50% or more starch to the binder enabled formation of airtight packages in the VFFS packaging trials.

[0368] 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 (2) comprising a paper (2a) comprising cellulose-containing natural fibres, wherein a grammage of the support layer (2) is preferably in a range between 35 g / m2and 130 g / m2, the support layer (2) further comprising a first precoating layer (3) on a first side of the paper (2a), wherein a grammage of the first precoating layer (3) is in a range between 1 g / m2and 10 g / m2, and applying a barrier-supporting coating composition (7) in form of an aqueous dispersion on the support layer (2), the aqueous dispersion preferably having solids content from 45 to 62 wt.%, thereby forming a barrier-supporting coating layer (4), the barriersupporting coating layer (4) having a coat weight of 2 to 15 g / m2and comprising binding agents at least 20 wt.% of a total dry weight of the barrier-supporting coating layer (4), wherein a first binding agent of the barrier-supporting coating composition(7) is selected from non-thermoplastic polymers, and a second binding agent of the barrier-supporting coating composition (7) is selected from thermoplastic polymers styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, polyesters and their mixtures, wherein a ratio of the first binding agent to the second binding agent is preferably from 0.5:1 to 5:1 , more preferably at least 1.1 :1 , applying a barrier coating composition (8) in form of an aqueous dispersion on the barrier-supporting coating layer (4), thereby forming a barrier coating layer (5), the barrier coating layer (5) having a coat weight of 3 to 12 g / m2, the barrier coating composition (8) comprising dispersed heat sealable polymer(s) at least 40 wt.%, wherein the dispersed heat sealable polymer(s) is / are selected from- acrylates,- ethylene-acrylic acid copolymers,- styrene-acrylate copolymers,- styrene-butadiene copolymers,- polyolefins,- polyesters, andtheir mixtures.

2. A heat sealable packaging material (1 ) comprisingA) a support layer (2) comprising a paper (2a) comprising cellulose- containing natural fibres, the support layer (2) further comprising a first precoating layer (3) on a first side of the paper (2a), wherein a grammage of the first precoating layer (3) is in a range between 1 g / m2and 10 g / m2, and a grammage of the support layer (2) is preferably in a range between 35 g / m2and 130 g / m2,B) a barrier-supporting coating layer (4) having a coat weight of 2 to 15 g / m2and comprising binding agents at least 20 wt.% of total dry weight of the barrier-supporting coating layer (4), wherein a first binding agent of the barrier-supporting coating layer is selected from non-thermoplastic polymers, and a second binding agent of the barrier-supporting coating layer is selected from styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, polyesters, and their mixtures, wherein a ratio of the first binding agent to the second binding agent is preferably from 0.5:1 to 5:1 , more preferably at least 1.1 :1 , andC) a barrier coating layer (5) having a coat weight of 3 to 12 g / m2and comprising heat sealable polymer(s) at least 40 wt.% of total dry weight of the 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.

3. The method according to claim 1 or the heat sealable packaging material according to claim 2, wherein the barrier-supporting coating layer (4) is situated between the first precoating layer (3) and the barrier coating layer (5).

4. The method or the heat sealable packaging material according to any of the preceding claims, wherein the first binding agent of the barriersupporting coating layer is selected from starches, hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures.

5. The method or the heat sealable packaging material according to any of the preceding claims, wherein the barrier-supporting coating layer (4) has a mineral pigment content from 20 wt.% to 80 wt.%, and / or the barrier coating layer (5) has a mineral pigment content from 0 wt.% to 60 wt.%.

6. The method or the heat sealable packaging material according to any of the preceding claims, wherein the ratio of the first binding agent to the second binding agent is in the range from 0.5:1 to 5:1 , more preferably from 0.6:1 to 4:1 , and still more preferably more than 1.1 :1.

7. The method or the heat sealable packaging material according to any of the preceding claims, wherein- the support layer (2) further comprises a second precoating layer (6) on a second side of the paper (2a), a grammage of the second precoating layer (6) being in a range between 0.5 g / m2and 7 g / m2,- optionally, the heat sealable packaging material comprises an additional coating layer on the second precoating layer (6), the additional coating layer preferably comprising one or more pigments, and one or more binders selected from styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, and their mixtures.

8. The method or the heat sealable packaging material according to any of the preceding claims, wherein the first binding agent comprises at least one of the starch and hemicellulose.

9. The method or the heat sealable packaging material according to any of the preceding claims, wherein the first binding agent comprises at least one of the polyvinyl alcohol and ethylene-vinyl alcohol copolymer.

10. The method or the heat sealable packaging material according to any of the preceding claims, wherein the second binding agent comprises at least one of the styrene-acrylate copolymer and styrene-butadiene copolymer.

11. 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.

12. 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.

13. 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, ethylene-acrylic acid copolymers, and polyolefins.

14. The method or the heat sealable packaging material according to claim 13, wherein the heat sealable polymer(s) is / are selected from styreneacrylate copolymers and styrene-butadiene copolymers.

15. The method or the heat sealable packaging material according to any of the preceding claims, wherein the heat sealable packaging material (1 ) is free of synthetic fibers, viscose and aluminum and, optionally, free of nanocellulose.

16. 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 equal to or less than 13 g / m*day.

17. 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 150 g / m2*day, determined at 23°C and 85% RH according to standard ISO 2528.

18. 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 40 hours, determined according to standard ASTM F119-82 at 40°C by using chicken fat.

19. 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 500 ms dwell time at 6 bar operating sealing pressure, and / or the heat sealable packaging material (1 ) is heat sealable at 150°C determined by using 700 ms dwell time at operating 6 bar sealing pressure.

20. 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 Cepi Recyclability Test Method Version 2, Oct 7, 2022.21 . A package, preferably a flexible package, comprising the heat sealable packaging material (1 ) according to any of the preceding claims 2 to 20.

22. A use of the heat sealable packaging material (1 ) according to any of the preceding claims 2 to 20 in a flexible packaging.

23. A use of a barrier-supporting coating layer (4) comprising- a first binding agent selected from non-thermoplastic polymers, preferably from starches, hemicelluloses, polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and their mixtures, and- a second binding agent selected from styrene-acrylate copolymers, styrene-butadiene copolymers, acrylates, polyesters, and their mixtures, wherein a ratio of the first binding agent to the second binding agent is preferably from 0.5:1 to 5:1 , for lowering a sealing temperature of a heat sealable packaging material comprising a heat sealable barrier coating layer comprising one or more polymers selected from acrylates, ethylene-acrylic acid copolymers, styrene-acrylate copolymers, styrene-butadiene copolymers, polyolefins, polyesters, and their mixtures.

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