Field of the invention

The invention relates to a packaging material and a package. The invention further relates to a method for manufacturing a packaging material.

Background of the invention

In industry, a large variety of packaging materials is manufactured, from which packages are made for products to be packaged. The properties and the desired shelf life of the products to be packaged typically determine the packaging material used for packaging each product.

The packaging materials may vary between different products and also within the same product group. In industry, however, there is still need for new packaging materials and packages.

Brief summary of the invention

It is an aim of this specification to present a packaging material and a package. Furthermore, it is an aim of this specification to present a method for manufacturing a packaging material.

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

A package can comprise a packaging material comprising: a support layer comprising or consisting of a paper or a paperboard comprising cellulose-containing natural fibers, the support layer having a first side and a second side, and a barrier coating layer on the first side of the support layer, wherein the barrier coating layer comprises polymeric material comprising a polymer having hydroxy acid derived repeating units, said hydroxy acid derived repeating units comprising at least 2 and equal to or less than 7 carbon atoms, wherein the polymeric material has a glass transition temperature at equal to or below 23°C.

The polymer having hydroxy acid derived repeating units comprising 2 to 7 carbon atoms may be composed of C2 to C7 hydroxy acid-derived repeating units such as glycolic acid, lactic acid, hydroxybutanoic acid, hydroxyvaleric acid, hydroxyhexanoic acid, and/or hydroxy heptanoic acid.

The hydroxy group in the hydroxy acid units may be in a, 0, y, 5, £, or imposition. The hydroxy acid units may be of either D or L enantiomer, or racemic mixtures.

In an advantageous embodiment, the polymer having hydroxy acid derived repeating units comprises glycolic acid units, hydroxycaproic acid units and lactic acid units.

Most preferably, the polymer having hydroxy acid derived repeating units comprises or consists of poly(glycolide-co-lactide-co-RI ) polymer(s), wherein R1 is selected from a group consisting of C4 to C7 lactones. Thus, the polymeric material can comprise poly(glycolide-co-D,L-lactide-co-R1 ) polymer(s), wherein R1 is selected from a group consisting of C4 to C7 lactones.

The packaging material comprises a support layer comprising a paperboard or paper that contains cellulose-containing natural fibers, and a barrier coating layer on the support layer.

In an advantageous embodiment, the support layer comprises or consist of the paper. Further, the barrier coating layer comprises a polymeric material comprising poly(glycolide-co-D,L-lactide-co-R1 ) polymer(s), wherein R1 is selected from a group consisting of C4 to C7 lactones. A method for manufacturing a packaging material can comprise the following steps: supplying a support layer, which can a paper or paperboard comprising cellulose-containing natural fibers, the support layer having a first side and a second side, and applying a barrier coating on the first side of support layer, which barrier coating is an aqueous dispersion comprising a polymeric material, thereby obtaining a barrier coating layer, wherein the polymeric material comprises a poly(glycolide-co-D,L- lactide-co-R1 ) polymer, wherein R1 is selected from a group consisting of C4 to C7 lactones, wherein the polymeric material has a melting temperature in a range between 70°C and 120°C and a glass transition temperature at equal to or below 23°C.

The polymeric material is preferably a semi-crystalline material. Said crystallinity can enable the polymeric material to be flexible at ambient temperature, without being sticky.

In addition to the polymer having hydroxy acid derived repeating units, the barrier coating can contain additives, such as plasticizers or waxes, to lower a melting point of the polymeric material.

As discussed, the polymeric material can comprise one or more poly(glycolide- co-D,L-lactide-co-R1 ) polymer(s), wherein R1 is selected from a group consisting of C4 to C7 lactones.

The glycolic acid in the poly(glycolide-co-D,L-lactide-co-R1 ) polymer can improve technical properties of the polymer.

Lactic acid is advantageous component for the polymer in order to obtain improved properties. Thanks to the lactic acid in the polymer, melting temperature of the polymeric material can be decreased. The lactic acid can further be a cost-effective component for the polymer. Still further, lactic acid can improve crystallinity level of the polymer. Lactones are a group of cyclic carboxylic esters. R1 component can be any one of C4 to C7 lactone, comprising 4 to 7 carbon atoms. R1 is preferably C6 lactone, comprising 6 carbon atoms. R1 can be caprolactone. Most preferably, R1 is £-caprolactone. Thanks to the R1 component that is selected from a group consisting of said C4-C7 lactones, and particularly if R1 is the caprolactone, glass transition temperature of the polymer can be substantially decreased.

Thus, the polymeric material can comprise glycolic acid-based polymer comprising certain monomers. However, not all glycolic acid-based polymers are as useful for barrier layer as the poly(glycolide-co-D,L-lactide-co-R1 ) polymers. For example, poly(lactide-co-glycolide) and poly(glycolide-co- caprolactone) polymers as such may not be as advantageous polymers to form a barrier layer on a paper or paperboard at a paper machine as the poly(glycolide-co-D,L-lactide-co-R1 ) polymer. Said poly(glycolide-co-D,L- lactide-co-R1 ) polymer is capable of forming an improved barrier layer on a surface of a paper or paperboard at typical process temperatures on paper machines.

In an embodiment, the polymer having hydroxy acid derived repeating units is a poly(glycolide-co-lactide-co-caprolactone). The polymeric material comprising poly(glycolide-co-lactide-co-caprolactone) is capable of forming an improved barrier layer having some good properties at typical process temperatures on paper machines. Most preferably, the caprolactone of the poly(glycolide-co-lactide-co-caprolactone) is E-caprolactone.

The polymeric material can comprise poly(glycolide-co-lactide-co-RI ) polymer. Surprisingly, a poly(glycolide-co-lactide-co-RI ) polymer, such as poly(glycolide-co-D,L-lactide-co-caprolactone), optionally with additives, can have good properties for forming such an aqueous dispersion with water which improves properties for coating purposes of a paper or paperboard in order to obtain a barrier layer having predetermined barrier properties.

For feasible operation on paper machines or paper coating machines, polymer(s) applied onto the paper or paperboard are preferably in a form of aqueous dispersion. The aqueous dispersion can have a solid content in a range between 30% and 50%. The poly(glycolide-co-lactide-co-RI ) polymer can have good properties for forming such an aqueous dispersion with water which has good properties for coating purposes of a paper or paperboard in order to obtain a barrier layer having predetermined barrier properties. In an embodiment, the aqueous dispersion has pH in a range between 4 and 10, preferably in a range between 5 and 9.

The barrier coating layer can be a coating layer comprising thermoplastic polymeric material having a melting temperature and/or film forming temperature in a range between 70°C and 120°C, and a glass transition temperature at equal to or below 23°C. Thus, the barrier coating can comprise polymeric material suitable to be used at typical process temperatures in dispersion coating of a paper machine. Further, thanks to said glass transition temperature, the barrier coating layer is not cracking too easily.

The polymer having hydroxy acid derived repeating units can be poly(glycolide-co-lactide-co-RI ) polymer, preferably poly(glycolide-co-D,L- lactide-co-caprolactone), with a glycolic acid content in a range between 50 mol-% and 87 mol-%, preferably equal to less than 85 mol-%, a lactic acid content in a range between 5 mol-% and 30 mol-%, and

R1 (such as caprolactone) content in a range between 5 mol-% and 30 mol-%.

Said selection of components can result in properties suitable for the purpose of paper coating in order to provide excellent barrier properties with truly biodegradable polymer.

Preferably, the barrier coating layer comprises poly(glycolide-co-D,L-lactide- co-caprolactone) with a glycolic acid content in a range between 50 mol-% and 85 mol-%, a lactic acid content in a range between 5 mol-% and 30 mol-%, and a caprolactone content in a range between 5 mol-% and 30 mol-%.

In an embodiment, the barrier coating comprises, in addition to the poly(glycolide-co-D,L-lactide-co-R1 ) polymer, a poly(glycolic acid-co-lactic acid) polymer, and/or a poly(glycolic acid-co-caproic acid) polymer. In this embodiment, a total amount of these polymers can be in a range between 5 wt.% and 70 wt.%, preferably at least 10 wt.%, calculated from the total dry weight of the barrier coating layer. Thus, the barrier properties of the barrier coating layer as well as processability of the barrier coating can be improved.

In an advantageous embodiment, pigment content of the barrier coating is close to critical pigment volume concentration (CPVC), which depends on the pigment type and aspect ratio. CPVC can vary, e.g., between 54-69 v-%. With typical densities of the polymers and typical pigments, this corresponds to 70- 81 w-% of pigments.

Pigment content of the barrier coating can be equal to or less than 80 wt.%, preferably equal to or less than 75 wt.%, more preferably equal to or less than 70 wt.%, and most preferably equal to or less than 65 wt.%, calculated from the total dry weight of the barrier coating layer. In an embodiment, the barrier coating layer comprises pigments in a range between 35 wt.% and 75 wt.%, calculated from total dry weight of the barrier coating layer. Sufficient amount of formulated polymer is required, for example, to fill all voids between pigment particles. Meanwhile, adding pigment is beneficial by increasing the solids content and decreasing cost. It can also improve barrier properties by making diffusion paths longer due to increased tortuosity. Thus, total amount of said polymeric material in the barrier coating layer can be at least 20 wt.%, preferably at least 25 wt.%, and more preferably at least 30 wt.%, calculated from the total dry weight of the barrier coating layer.

A total amount of poly(glycolide-co-D,L-lactide-co-R1 ) polymers can be at least 60 wt.%, preferably at least 65 wt.%, more preferably at least 70 wt.%, and most preferably at least 75 wt.%, calculated from total dry weight of organic material in the barrier coating. Technical effect is to provide a coating layer with excellent barrier properties, with truly biodegradable polymer, which can be biodegradable even in marine and soil environment.

In an embodiment, total amount of poly(glycolide-co-D,L-lactide-co- caprolactone)s can be at least 60 wt.%, preferably at least 65 wt.%, more preferably at least 70 wt.%, and most preferably at least 75 wt.%, calculated from total dry weight of organic material in the barrier coating. Technical effects include obtaining barrier coating layer having good properties for dispersion coating on a paper machine, providing good film forming properties with low tackiness level. Furthermore, the poly(glycolide-co-D,L-lactide-co- caprolactone)s can be biodegradable even in marine and soil environment.

Total amount of pigment particles, and poly(glycolide-co-D,L-lactide-co-R1 ) polymers in the barrier coating can be at least 75 wt.%, preferably at least 80 wt.%, more preferably at least 85 wt.%, and most preferably at least 90 wt.%, calculated from the total dry weight of the barrier coating layer. The barrier coating can further comprise additives, for example waxes and/or plasticizers, to adjust the thermal properties of the formulation.

The polymeric material can comprise or consist of poly(glycolide-co-D,L-lactide-co-R1 ) polymer(s), and optionally, additive(s) to modify the thermal properties.

In an advantageous embodiment, the polymeric material contains at least one additive for modifying the thermal properties. An amount of said additive(s) can be in a range between 5 wt.% and 30 wt.%, calculated from total dry weight of the polymeric material. Technical effect of additive(s) is to provide an effective route to modify thermal and/or mechanical properties of the barrier coating. Further, thanks to the additive(s), a melting temperature of the polymeric material can be decreased.

The poly(glycolide-co-D,L-lactide-co-R1 ) polymer, such as poly(glycolide-co- D,L-lactide-co-caprolactone), if used, can have a molecular weight in a range between 5 000 g/mol and 200 000 g/mol, preferably in a range between 10 000 g/mol and 100 000 g/mol. Technical effect for the molecular weight is to provide polymer(s) that is/are stable during processing and shelf time of packed products.

Thanks to the novel solution, it is possible to obtain a predetermined temperature for film forming and fusion of the polymer. This can help to manufacture the barrier coating layer at a paper machine. The barrier coating layer can be arranged to have a glass transition temperature below 23°C, preferably below 20°C, more preferably below 10°C, and most preferably below 5°C. Technical effect is that flexibility of the barrier coating can be improved so that the packaging material comprising said coating can be, e.g., folded around an object so that the barrier coating is not broken but maintains its barrier properties. Therefore, the barrier coating layer is not easily broken during usage of the packaging material. Below glass transition temperature, polymers are typically rigid and brittle (glass-like). A polymer can therefore be flexible only above its glass transition temperature. Preferably, the glass transition temperature is lower than ambient temperature.

The packaging material can have a support layer comprising or consisting of a paper or paperboard having a grammage in a range between 20 g/m ² and 110 g/m ² . The grammage of the paper or paperboard is preferably in a range between 35 g/m ² and 100 g/m ² , more preferably between 45 g/m ² and 90 g/m ² . Technical effect is to obtain packaging material having good strength properties as well as substantially light weight. It is good for manufacturing and transportation costs to reduce the grammage of the paper or paperboard to reduce the weight of the packaging material and, thus, the weight of the package. However, typically paper having less grammage is also thinner and may have reduced strength properties.

The packaging material can have a grammage in a range between 25 gsm and 120 gsm. The packaging material can have a grammage of at least 30 gsm, preferably at least 40 gsm. Further, the packaging material can have a grammage equal to or less than 120 gsm, preferably equal to or less than 100 gsm. The grammage of the packaging material can advantageously be e.g. in a range between 45 gsm and 90 gsm, or in a range between 60 gsm and 100 gsm. Technical effect is to obtain packaging material having suitable properties as well as decreased manufacturing and transportation costs.

The packaging material can comprise or consist of a paper or paperboard, and a barrier coating layer on at least one side of the paper or paperboard. The support layer, such as the paper of paper board, has a first side and a second side, and the barrier coating layer preferably covers at least one of the sides of the support layer for obtaining the predetermined barrier properties.

The paper or paperboard is preferably a sized and/or pigment coated paper, i.e., it preferably has a coating layer on its surface. Thus, it is possible to achieve full surface coverage with lower coat weight of the barrier coating. The paper or paperboard is preferably pigment coated paper in order to further improve barrier properties of the packaging material.

For environmental reasons, the paper or paperboard may comprise recycled fibers (RCF) e.g. in a range between 10 wt.% and 80 wt.%, preferably in a range between 20 wt.% and 60 wt.%, calculated from the total weight of the fibers in the paper or paperboard. In an embodiment, the paper/paperboard does not have said recycled fibers.

The paper or paperboard can comprise mineral fillers in a range between 0 wt.% and 35 wt.%, preferably in a range between 5 wt.% and 25 wt.%, calculated from the total weight of the paper or paperboard. The usage of the mineral fillers can improve some properties of the paper or paperboard as well as decrease the manufacturing costs of the paper or paperboard. However, the mineral fillers typically decrease strength properties of the paper. Thus, preferably, the mineral filler content of the packaging material is not very high.

The poly(glycolide-co-D,L-lactide-co-R1 ) polymer can be capable of marine biodegradation. Thus, packaging material comprising or consisting of

A) paper or paperboard comprising cellulose-containing natural fibers, and

B) a barrier coating layer comprising poly(glycolide-co-D,L-lactide-co-R1 ) polymer, can be environmentally friendly alternative for other kind of barrier materials.

As discussed, the packaging material comprises at least one barrier coating layer. In an embodiment, in order to decrease the manufacturing costs, the packaging material comprises only one barrier coating layer comprising the polymer having hydroxy acid derived repeating units. In an advantageous embodiment, the packaging material comprises or consist of: a paper or paperboard, preferably comprising one or more than one pigment coating layer, and only one barrier coating layer comprising the polymer having hydroxy acid derived repeating units, such as poly(glycolide-co-D,L-lactide-co- R1 ) polymer, on the paper or paperboard.

The barrier coating layer may comprise poly(glycolide-co-D,L-lactide-co-R1 ) polymer only on one side of the paper or paperboard. Technical effect is to provide suitable barrier properties cost efficiently.

In an embodiment, the polymeric material has a melting temperature below 120°C, wherein the melting temperature is determined based on melting of the polymer powder in an oven. In a typical paper machine, or paper coating machine, paper web may pass through a drying section within seconds after coating application, and the polymer particles in coating layer may need to fuse together into a film within this timeframe. Low enough melting point enables fast film forming, which can be required in dispersion coating processes.

The barrier coating layer can have a coat weight in a range between 1 g/m ² and 30 g/m ² when measured as a dry weight of the barrier coating layer. The content of the barrier coating can be, for example, 1 to 20 g/m ² , preferably 2 to 15 g/m ² , more preferably 3 to 10 g/m ² , and most preferably from 4 to 9 g/m ² , when measured as a dry weight of the barrier coating layer. Technical effect is to provide improved protection from water, e.g. at a temperature of 25°C, with the packaging material. The coat weight can depend on polymers and pigments used in the barrier coating, and a thickness of the barrier coating layer.

A thickness of the barrier coating layer can be in a range between 0.8 pm and 20 pm. The thickness of the barrier coating layer is preferably at least 1 pm, such as between 1 to 15 pm, and more preferably at least 2 pm, such as between 2 pm and 12 pm, and most preferably at least 3 pm, such as 3 to 10 pm. Further, the thickness of the barrier coating can be equal to or less than 20 pm, more preferably equal to or less than 15 pm, such as 3 pm to 15 pm, and most preferably equal to or less than 10 pm, such as 2 pm to 9 pm. Thus, good barrier properties, such as a protection from water vapor, can be obtained cost efficiently with the packaging material.

Glycolic acid-based polymers according to this specification can be used to formulate polymeric material suitable for preparation of aqueous polymer dispersion for barrier coating of fiber-based products, the aqueous polymer dispersion having a melting point in a range between 70°C and 120°C, and a glass transition temperature at equal to or below 23°C. Thus, an aqueous dispersion according to the specification may comprise a mixture having a polymeric material having a melting point in a range between 70°C and 120°C, the aqueous dispersion being suitable for forming a barrier coating layer for a fiber-based product, which barrier coating layer may have a glass transition temperature at below 23°C.

The packaging material according to the specification can be used, e.g., in a food package. Thus, a package comprising the packaging material may be, for example, a food package.

A high variation of polymers comprising combinations of hydroxy acid-derived repeating units with wide differences in properties exist. It was surprising and unexpected that the claimed barrier coating comprising the poly(glycolide-co- D,L-lactide-co-R1 ) polymer, wherein R1 is selected from a group consisting of C4 to C7 lactones, shows good barrier properties combined with suitable film formation temperature for the application of dispersion barrier coating. Surprisingly, the claimed coating shows a combination of suitable water vapor barrier for many applications, e.g., for food packaging, as well as suitable film formation at temperature of paper machines.

As discussed, the polymeric material may comprise hydroxy acid-derived repeating units having low chain length, the low chain length referring to a chain length of 2 to 7 carbon atoms.

Conventionally, this kind of barrier coatings comprising e.g. glycolic acid-based polymer(s) have not been used in paper machines due to high melting point of the polymers. For example, typically polymeric materials having a melting point above 120°C cannot be used efficiently at paper machines, because web temperatures of paper machines are typically less than 100°C. Further, discoloration of paper starts to occur at temperatures exceeding 150°C. Still further, coatings having too high temperature might “boil” water from the paper. Thus, web temperatures equal to or below said 120°C, and particularly below 105°C are preferred to avoid blistering caused by water evaporating inside the coating layer. The blistering is particularly harmful for barrier papers as even microscopic pinholes in the coating layer can severely damage barrier properties of the obtained paper. Further, if the coating is too hot, the obtained paper may become too dry.

Furthermore, some challenges may be 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.

Thanks to the present invention, it is possible to obtain a novel packaging material, which can be used as a protective packaging. With the present invention, several advantages can be obtained, such as a suitable protection from water. The novel barrier coating can protect a product, such as food, from humidity, water and/or oxygen. Further, the novel barrier coating can prevent grease penetration.

In an embodiment, the packaging material is used for flexible packaging products. Thus, the barrier coating layer can be arranged to be flexible. Barrier layers in flexible packaging products may have to withstand folding during the packaging process, transport, and handling. Thus, in order to avoid cracking at least at room temperature, the barrier coating layer can be flexible.

Thus, the barrier coating layer may be used on packages having folded surfaces. The packaging material having the barrier coating layer, if being flexible, can be foldable so that it can be folded, without cracking, at a temperature of 23°C, preferably at a temperature of 10°C. Moreover, the packaging material having the barrier coating layer, if it is flexible, may be thereafter turned back to the planar form at a temperature of 23°C, preferably at a temperature of 10°C, without cracking. The packaging material may be printable by a printing technique according to the state of art. Thus, the barrier coating layer can be arranged to be printable.

The packaging material according to the invention as well as the package according to the invention can be manufactured in an environmentally friendly way so that polymers of the barrier coating layer can be capable of even marine biodegradation.

Packaging is a huge polymer processing industry, and plastic pollution is a significant environmental burden. The novel dispersion coating can be solution to the huge environmental problems caused by plastics. By using the claimed barrier coating layer instead of other packaging polymers, many environmental related problems can be solved. The novel barrier coating can be used e.g., for reduction in CO ² emissions by utilizing glycolic or lactic acid obtained from renewable raw materials. Still further, polymers of the barrier coating can have high biodegradability in different environments, not just e.g., in composting plants. Thus, several environmental related problems can be avoided.

As discussed, the barrier coating layer according to the invention can have high biodegradability in different environments, not just in composting plants. Vulnerable marine environments suffer greatly from microplastics. Thanks to the novel solution, it is possible to obtain barrier coating that degrades fast after use, even in marine environments. Conventional solutions for barrier coatings have not been easily biodegradable, if accidentally released to nature, but they may have accumulated e.g., in the marine environment as debris and microplastics.

Description of the drawings

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

Fig 1 shows an example of a packaging material in cross-section,

Fig. 2 shows a package according to an embodiment,

Fig. 3 shows reduced schematic chart of an example for manufacturing packaging material, and Fig. 4 shows, as an example, a schematic copolymerization reaction scheme of glycolide, lactide, and £-caprolactone.

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

Detailed description

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

1 package,

2 packaging material comprising a barrier coating layer,

5 support layer comprising a paper or paperboard,

6a barrier coating,

6 barrier coating layer, and

10 barrier coating unit.

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

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

1 ) Grammage ISO 536

2) Water absorption ISO 535: Cobb 300s

3) WVTR ISO 2528:115 or modified ASTM F1249-13

4) OTR Modified ASTM F1927-14

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

The modified conditions of said modified ASTM F1249-13 are as follows:

Samples are conditioned at 23 °C and 50% relative humidity prior to testing. Two to four specimens from each film or coated paper sample are tested. Test cells with a diffusion area of 5.64 cm ² are used or specimens are masked with foils providing a diffusion area of 5 cm ² . The test specimens are cut to approximately 7 cm by 7 cm for the test cell with a reduced diffusion area and approximately 5 cm by 5 cm for the specimens masked with foils. Tests are carried out at 23 °C. Carrier gas is dry, and the relative humidity of test gas is 85%. Uncoated side or paper specimens is mounted facing the high humidity side of the diffusion cells.

The term ‘OTR’ refers to oxygen transmission rate, i.e. oxygen barrier at conditions of RH 50%, temperature 23°C.

The modified conditions of the modified ASTM F1927-14 are as follows:

Samples are conditioned at 23 °C and 50% relative humidity prior to testing. Two to four specimens from each film or coated paper sample are tested. Test cells with a diffusion area of 5.64 cm ² are used or specimens are masked with foils providing a diffusion area of 5 cm ² . The test specimens are cut to approximately 7 cm by 7 cm for the test cell with a reduced diffusion area and approximately 5 cm by 5 cm for the specimens masked with foils. Tests are carried out at 23 °C. Both carrier gas (98% nitrogen, 2% hydrogen) and test gas (100% oxygen) have relative humidity of 50%. Coated side of paper specimens is mounted facing the carrier gas flow in the diffusion cells.

Further, the following methods can be used in obtaining stated values of parameters:

The composition of the polymer can be determined using nuclear magnetic resonance (NMR) spectroscopy. The measurements can be performed with Bruker AVANCE III 500 MHz using 5 mm BBFO double resonance, broad band optimized probe. The samples are prepared by dissolving approximately 100 mg of polymer in 1 mL of hexafluoroisopropanol. After the solution is visually homogenous, 0.5 mL of 0.1 M chromium(lll) acetylacetonate solution in deuterated chloroform is added. The samples are stirred with a magnetic stirrer at least overnight prior to measurements. The monomer ratios are measured using quantitative ¹³ C experiments. Molar masses can be measured with size exclusion chromatography (SEC) using 1 ,1 ,3,3, 3-hexafluro-2-propanol (HFIP) with 5mM sodium trifluoroacetate as the eluent. Waters styragel HR-4E and HR 5 columns with a pre-column are used (0,5 ml/min, T=40 °C). The elution curves are detected using Waters 2414 Refractive index detector. The molar mass distributions (MMD) are calculated against 9 x polymethylmethacrylate (PMMA, (Agilent), 2710 - 1 667 000 g/mol) standards in HFIP, using 3rd order fit (R ² = 0.998-0.999) and Waters Empower 3 software.

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

1 . Dynamic phase from 0 °C to 110 °C

2. Isothermic phase at 110 °C, 60 min

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

4. Isothermic phase at 240 °C, 2 min

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

6. Isothermic phase at 0 °C, 2 min

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

8. Isothermic phase at 240 °C, 2 min

9. Dynamic phase from 240 °C to 20 °C

DSC, method for terpolymers:

Dynamic heating rate of 10 C/min. segments:

1 . Isothermic phase at 0 C, 2 min

2. Dynamic phase from 0 C to 240 C (First heating)

3. Isothermic phase at 240 C, 2 min

4. Dynamic phase from 240 C to -50 C (First cooling)

5. Isothermic phase at -50 C, 2 min

6. Dynamic phase from -50 C to 240 C (Second heating)

7. Isothermic phase at 240 C, 2 min

8. Dynamic phase from 240 C to 25 C The term ‘gsm’ refers to grams per square meter (g/m ² ). Unless otherwise expressed, all the grammages are in dry weight.

The term “polymer having hydroxy acid derived repeating units” refers to the poly(glycolide-co-D,L-lactide-co-R1 ) polymer, wherein R1 is selected from a group consisting of C4 to C7 lactones.

The term ‘barrier coating’ refers to a coating to be applied onto a support layer, such as onto a paper or paperboard, which coating contains the poly(glycolide- co-D,L-lactide-co-R1 ) polymer, wherein R1 is selected from a group consisting of C4 to C7 lactones. The barrier coating can be applied as an aqueous dispersion.

The term ‘barrier coating layer’ refers to a coating layer on a support layer, which support layer is typically a paper or paperboard, which barrier coating layer contains the poly(glycolide-co-D,L-lactide-co-R1 ) polymer, wherein R1 is selected from a group consisting of C4 to C7 lactones.

The barrier coating layer can be formed from the barrier coating, which coating is preferably aqueous dispersion comprising the poly(glycolide-co-D,L-lactide- co-R1 ) polymer, wherein R1 is selected from a group consisting of C4 to C7 lactones.

The term ’paper or paperboard’ can refer to any paper comprising cellulose- containing natural fibers or any paperboard comprising cellulose-containing natural fibers, typically as its main raw material. Further, the paper as well as the paperboard 5 can comprise, for example, one or more fillers and/or additives.

The paper or paperboard 5 preferably has a coating layer comprising pigments on its surface(s). Thus, the support layer preferably comprises or consists of the paper or paperboard having a coating layer comprising pigments on its surface(s). Technical effect is to significantly improve properties of the packaging material.

The paper or paperboard 5 may be, e.g., a pigment coated wood free paper. In an example, the paper or paperboard 5 is one side coated paper having a pigment coating layer on one side of the paper or paperboard. In an example, the paper or paperboard has a pigment coating layer on both sides of the paper or paperboard. Said pigment coating layer refers to a coating layer comprising pigment(s), which layer does not comprise said poly(glycolide-co-D,L-lactide- co-R1 ) polymer, wherein R1 is selected from a group consisting of C4 to C7 lactones.

The term ‘cellulose-containing natural fiber’ refers to any plant material that contains cellulose.

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

Preferably, the paper or paperboard 5 comprises cellulose-containing natural fibers which are of wood origin. The paper or paperboard 5 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.

The paper (or paperboard) may comprise recycled cellulose-containing natural fibers from 0 wt.% up to 100 wt.%, determined from all cellulose-containing fiber sources in the paper or paperboard. The amount of the recycled cellulose- containing fibers in the paper (or paperboard) may be at least 5 wt.%, for example at least 10 wt.%, from all cellulose-containing fiber sources in the paper (or paperboard). Thus, it can be possible to decrease the manufacturing costs of the product. Further, the usage of the cellulose-containing recycled fibers can reduce the needed amount of the virgin fibers, hence, this can be environmentally friendly solution. Still further, in some cases, the usage of cellulose-containing recycled fibers can reduce water pollution and/or air pollution. In an embodiment, the amount of cellulose-containing recycled fibers in the paper (or paperboard) is less than 50 wt.%, more preferably less than 20 wt.%, and most preferably equal to or less than 15 wt.%, calculated from all cellulose-containing fiber sources. With virgin fibers, it can be easier to obtain wanted properties, compared to products with recycled fibers.

An example of a polymer having hydroxy acid derived repeating units is a terpolyester. There are many known terpolyesters with different polymer structures. Terpolyesters differ in their properties depending e.g. on their chemical composition, or length of the monomer units. Thus, not all terpolyesters have same properties. Further, not all terpolyesters can be used for similar products.

The barrier coating comprises the poly(glycolide-co-D,L-lactide-co-R1 ) polymer, wherein R1 is selected from a group consisting of C4 to C7 lactones, such as poly(glycolide-co-D,L-lactide-co-caprolactone)(s). Poly(glycolide-co- D,L-lactide-co-R1 ) polymers can be environmentally friendly polymers. They are available by state-of-the-art polymerization technologies and can be rapidly biodegradable. It was surprising and unexpected that the claimed barrier coating comprising the poly(glycolide-co-D,L-lactide-co-R1 ) polymer, wherein R1 is selected from a group consisting of C4 to C7 lactones, shows good barrier properties combined with suitable film formation temperature for the application of dispersion barrier coating.

Figure 4 shows an example of a schematic copolymerization reaction scheme of glycolide, lactide, and £-caprolactone.

For example, poly(glycolide-co-D,L-lactide-co-caprolactone)s are environmentally friendly polymers that are available by state-of-the-art polymerization technologies such as ring-opening polymerization or polycondensation. Poly(glycolide-co-D,L-lactide-co-caprolactone)s can be rapidly biodegradable, and their biodegradation profile may be compared to cellulose. Surprisingly, a poly(glycolide-co-lactide-co-RI ) polymer, such as poly(glycolide-co-D,L-lactide-co-caprolactone), optionally with additives, can have good properties for forming such an aqueous dispersion with water which improves properties for coating purposes of a paper or paperboard in order to obtain a barrier layer having predetermined barrier properties.

Thus, the poly(glycolide-co-D,L-lactide-co-R1 ) polymer(s) can be produced by methods and raw materials known by a person skilled in the art. Raw materials may comprise, for example, glycolide and lactide from synthetic or biotechnical pathways. Furthermore, raw materials may comprise, for example, at least one of 8-caprolactone, y-butyrolactone, p-propiolactone, and 5-valerolactone.

For example, poly(glycolic acid) as such has high degree of crystallinity, brittleness and stiffness that are unsuitable for many applications. Furthermore, for example, some polyhydroxyal konates and polylactic acid can have similar challenges.

Technical effect of using other hydroxyacids in co-, ter, or multipolymers together with glycolic acid units to form poly(glycolide-co-D,L-lactide-co-R1 ) polymer is to improve flexibility, tensile strength, elongation at fracture, and thermal stability of the barrier coating.

Poly(glycolide-co-D,L-lactide-co-R1 ) polymers have shown improved thermal properties compared to poly(glycolic acid). Poly(glycolide-co-D,L-lactide-co- R1 ) polymers are able to provide advantageous crystalline structures providing barrier properties, the improved thermal properties meaning e.g. decrease in melting temperature and/or decrease in glass transition temperature.

In an embodiment, polymer particles in the barrier coating color have a particle diameter of less than 10 pm, preferably equal to or less than 6 pm, and most preferably equal to or less than 4 pm. Thanks to said particle size, uniformity and/or integrity of the formed barrier film may be improved. The term barrier coating color refers to the polymer(s) of the barrier coating in a solid state, before melting into the supplied barrier coating.

The barrier coating can be applied in the form of aqueous dispersion. Aqueous coatings can be applicable in state-of-the art paper mills and at converters for coating purposes. In an embodiment, the aqueous dispersion has a Brookfield viscosity (at 100 rpm) in a range from 100 mPas to 1000 mPas.

The barrier coating may comprise predetermined fraction of each unit in the poly(glycolide-co-D,L-lactide-co-R1 ) polymer, such as poly(glycolide-co-D,L- lactide-co-caprolactone), to optimize the properties in terms of film formation and barrier performance. The fraction of each unit can be varied to tailor the performance for different process conditions and end use applications. The poly(glycolide-co-D,L-lactide-co-R1 ) polymer can have a glycolic acid content of at least 50 mol-%, more preferably at least 60 mol-%, and most advantageously at least 65 mol-%, calculated from the poly(glycolide-co-D,L- lactide-co-R1 ) polymer. Preferably, a content of glycolic acid in the poly(glycolide-co-D,L-lactide-co-R1 ) polymer is equal to or less than 87% mol- %, more preferably equal to or less 86 mol-%, and most advantageously equal to or less 85 mol-%, calculated from the poly(glycolide-co-D,L-lactide-co-R1 ) polymer. Technical effect is that said fraction of glycolic acid can have huge effect on properties of the polymer. Thanks to said content of glycolic acid, barrier properties of the barrier coating can be improved. Further, this glycolic acid content can be particularly suitable in order to form such an aqueous dispersion with water which is suitable for coating purposes of a paper or paperboard.

Alternatively or in addition, the poly(glycolide-co-D,L-lactide-co-R1 ) polymer can have a lactic acid content of at least 5% mol-%, more preferably at least 8 mol-%, still more preferably at least 10 mol-%, and most advantageously at least 15 mol-%, calculated from the poly(glycolide-co-D,L-lactide-co-R1 ) polymer. Preferably, a content of lactic acid in the poly(glycolide-co-D,L- lactide-co-R1 ) polymer is equal to or less than 30% mol-%, more preferably equal to or less 25 mol-%, and most advantageously equal to or less 20 mol- %, calculated from poly(glycolide-co-D,L-lactide-co-R1 ) polymer. In an embodiment, a content of lactic acid in the poly(glycolide-co-D,L-lactide-co- R1 ) polymer is approximately 18 % mol-%, such as in a range between 15 mol- % and 20 mol-%. Thanks to said lactic acid content, melting temperature of the polymeric material can be decreased into the determined range. The lactic acid can also be a cost-effective component for the polymer. Still further, said lactic acid content can be particularly useful for improving crystallinity level of the polymer.

Alternatively or in addition to said glycolic acid content and/or to said lactic acid content, the poly(glycolide-co-D,L-lactide-co-R1 ) polymer can have R1 content of at least 5% mol-%, more preferably at least 9 mol-%, and most advantageously at least 12 mol-%, calculated from the poly(glycolide-co-D,L- lactide-co-R1 ) polymer. Preferably, a content of R1 in the poly(glycolide-co- D,L-lactide-co-R1 ) polymer is equal to or less than 30% mol-%, more preferably equal to or less than 25 mol-%, and most advantageously equal to or less 20 mol-%, calculated from the poly(glycolide-co-D,L-lactide-co-R1 ) polymer. Thanks to said R1 content, glass transition temperature of the polymer can be significantly decreased.

In an embodiment, the polymer is poly(glycolide-co-D,L-lactide-co- caprolactone), and a content of caprolactone in the poly(glycolide-co-D,L- lactide-co-caprolactone) polymer is as least 5% mol-%, more preferably at least 9 mol-%, and most advantageously at least 12 mol-%, calculated from the poly(glycolide-co-D,L-lactide-co-caprolactone) polymer. Preferably, a content of caprolactone in the poly(glycolide-co-D,L-lactide-co-caprolactone) polymer is equal to or less than 30% mol-%, more preferably equal to or less than 25 mol-%, and most advantageously equal to or less 20 mol-%, calculated from the poly(glycolide-co-D,L-lactide-co-caprolactone) polymer. Said content of caprolactone can be particularly suitable for decreasing glass transition temperature of the polymer.

Technical effect of said polymer(s) having the above mentioned contents of glycolic acid, lactic acid, and lactone components, is that the barrier coating can be capable of forming a barrier layer on a surface of a paper or paperboard at typical process temperatures on paper machines, which formed barrier layer can have improved barrier properties.

As discussed, the polymeric material of the barrier coating comprises poly(glycolide-co-D,L-lactide-co-R1 ) polymer(s).

Glass transition temperature of the barrier coating layer 6 comprising the polymeric material can be arranged to be below 23°C, preferably below 20°C, more preferably below 10°C, and most preferably below 5°C. Further, melting point of the polymeric material can be arranged to be in a range between 70°C and 120°C, more preferably in a range between 80°C and 105°C.

In an embodiment, film forming temperature of the polymeric material, optionally formulated with additives such as waxes or plasticizers, is in a range between 70°C and 120°C, more preferably in a range between 80°C and 105°C. The packaging material 2 can be arranged to provide a good water vapour transmission rate (WVTR) of less than 100 g/m ² /d, preferably less than 50 g/m ² /d, more preferably less than 20 g/m ² /d, and most preferably less than 10 g/m ² /d, to protect the packaged product.

Further, the packaging material 2 can be arranged to provide a good water resistance (Cobb (300 s) less than 10 g/m ² , preferably less than 5 g/m ² , and most preferably less than 1 g/m ² ).

Still further, the packaging material 2 can be arranged to provide an improved grease resistance and/or heat sealability.

Thus, the packaging material 2 and the package 1 can protect the packaged product from water and/or grease, and/or from water vapour. Further, the barrier coating layer, and particularly the poly(glycolide-co-D,L-lactide-co-R1 ) polymer(s) despite of these excellent properties, can be soil- and marine- biodegradable.

The barrier coating 6 can comprise, in addition to the poly(glycolide-co-D,L- lactide-co-R1 ) polymer(s), for example, fillers, such as mineral fillers, and processing aids, which can comprise, e.g., dispersing aids, and/or pH adjusting aids, and/or additives to tailor the thermal properties.

The barrier coating layer can comprise mineral fillers in a range between 0 wt.% and 80 wt.%, preferably in a range between 20 wt.% and 75 wt.%, and more preferably in a range between 30 wt.% and 70 wt.%, calculated from the total dry weight of the barrier coating layer. The usage of the mineral fillers can improve some properties of the packaging material as well as decrease the manufacturing costs of the product. However, the mineral content of the barrier coating layer may not be too high in order to obtain predetermined barrier properties. Mineral fillers can comprise, for example, at least one of: kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulphate, and titanium dioxide.

The barrier coating can comprise one or more than one additive, such as a plasticizer(s) or a wax(es), to modify the thermal properties. Amount of the additives can be in a range between 0 wt.% and 30 wt.%, calculated from total dry weight of the organic material in the barrier coating.

The plasticizer, if used, may comprise e.g. triethyl citrate, other citric acid esters, alkenyl succinic anhydride, or their mixtures, e.g., in a range between 0 and 15 wt.%, determined from total dry weight of the organic material of the barrier coating. The addition of plasticizers can be a relatively simple route to modify the thermal and mechanical properties of the barrier coating. Further, a decrease in processing temperature can be achieved. For example, blending poly(glycolide-co-D,L-lactide-co-R1 ) polymer with a plasticizer can modify the physical properties of poly(glycolide-co-D,L-lactide-co-R1 ) polymer.

The wax(es), if used, can comprise at least one of bio-based waxes such as bees wax, carnauba wax, rye bran wax, sunflower oil wax, bio-based or synthetic Fischer-Tropsch waxes, and synthetic waxes such as paraffin or polyethylene waxes.

Blending the polymer with a wax can modify the physical properties of the polymer. In an advantageous embodiment, the wax is selected so that the polymeric material is biodegradable.

As discussed, the additives can comprise dispersing aid(s). The dispersing aid(s) can comprise at least one of

- Polyvinyl alcohol,

- Ethylene vinyl acetate,

- Alcohol ethoxylate,

- Ethoxylated fatty acid, and

- Ethylene oxide-propylene oxide block copolymer.

The at least one dispersing aid is a substance, typically a surfactant, that is added to prevent coagulation or settling of the particles in the dispersion. Thus, the technical effect of these dispersing aids is to prevent coagulation or settling of the particles in the dispersion.

The additives can comprise pH regulation chemical(s). The pH regulation chemical(s) can comprise at least one of

- Ammonia - N-(2-Hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) (HEPES) buffer, and

- Phosphate and or hydrocarbonate buffer.

Technical effect of these pH regulation chemicals is to prevent the uncontrolled pH decrease of aqueous dispersions due to hydrolytic depolymerization of acidic monomers during processing.

By the selection of the poly(glycolide-co-D,L-lactide-co-R1 ) polymer(s) and

- mineral fillers and/or

- processing aids, used for the barrier coating layer, it can be possible to influence, for example, one or more of following properties of the packaging material 2: water vapour transmission rate, oxygen transmission rate, heat-sealability, adherence of the barrier coating to paper or paperboard, grease resistance, and number of pinholes.

The barrier coating 6a to be applied onto a paper (or paperboard) can be an aqueous dispersion comprising polymeric material comprising the poly(glycolide-co-D,L-lactide-co-R1 ) polymer(s).

In an embodiment, the barrier coating 6a to be applied onto a paper (or paperboard) is an aqueous dispersion comprising polymeric material comprising the poly(glycolide-co-D,L-lactide-co-R1 ) polymer(s), wherein R1 is C4-C7 lactone, such as poly(glycolide-co-D,L-lactide-co-caprolactone).

Advantageously, the barrier coating layer 6 is the topmost coating layer of the packaging material 2. However, there may be, for example, a printing on the barrier coating layer.

In an advantageous embodiment, said barrier coating layer is the only such coating layer of the packaging material 2 which comprises the poly(glycolide- co-D,L-lactide-co-R1 ) polymer(s). Grammage of the barrier coating layer can be at least 1 gsm, preferably at least 2 gsm, more preferably at least 3 gsm, and most preferably at least 4 gsm. Technical effect is to provide a barrier coating layer having good barrier properties. Further, grammage of the barrier coating layer can be equal to or less than 20 gsm, preferably equal or less than 15 gsm, more preferably equal to or less than 10 gsm, and most preferably equal to or less than 7 gsm. Technical effect is to provide a barrier coating layer having improved barrier properties cost efficiently. The grammage of the barrier coating layer 6 can be 1 to 20 gsm, preferably 2 to 12 gsm, more preferably from 3 to 10 gsm, and most preferably from 4 to 9 gsm, determined as a dry weight of the coating layer. Preferably, the barrier coating layer 6 consists of a single coating layer. Thus, it is possible to produce a packaging material 2 having improved properties in a cost-effective process.

It can be good for manufacturing and transportation costs to reduce the grammage of the paper or paperboard to reduce the weight of the packaging material 2 and, thus, the weight of the package 1. However, typically paper having less grammage is also thinner and can have reduced strength properties. Thus, the grammage of the paper or paperboard 5 is advantageously at least 35 gsm, more advantageously at least 40 gsm and not greater than 120 gsm, for example in a range between 40 gsm and 100 gsm. In an advantageous example, the grammage of the paper or paperboard 5 is between 45 gsm and 80 gsm. Thus, it is possible to decrease manufacturing costs of the packaging material 2. Further, transportation costs of the packaging material 2 as well as the transportation costs of the package 1 , can be decreased. Still further, the packaging material 2 can be environmentally friendly solution due to the minimum amount of raw materials needed for the package 1 . Further, it is possible to obtain packaging material having good strength properties together with substantially light weight.

As discussed, the paper or paperboard 5 can comprise mineral fillers. Mineral filler(s) can decrease the manufacturing costs of the paper or paperboard 5. Mineral fillers can comprise, for example, clay, calcined clay, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulphate, and/or titanium dioxide. In an embodiment, the total mineral filler content of the paper or paperboard 5 is 0 to 35%. The paper or paperboard 5 may not comprise more than 35 wt.% mineral fillers because mineral fillers can decrease strength properties of the product. The total mineral filler content of the paper or paperboard 5 is preferably equal to or less than 30%, such as in a range between 5 and 30%, more preferably equal to or less than 20%, such as in a range between 10% and 20%, and most preferably equal to or less than 15%. The strength properties of the packaging material 2 typically improve as the amount of mineral fillers decreases.

In an embodiment, the paper or paperboard 5 comprises precipitated calcium carbonate and/or ground calcium carbonate as a filler. Preferably, in this embodiment, said mineral filler content comprises calcium carbonate at least 50 wt.%, calculated from a total dry weight of the mineral fillers. Calcium carbonate can be cost effective mineral filler having suitable properties for the paper or paperboard 5.

The grammage of the packaging material 2 can be in a range between 25 gsm and 120 gsm, more preferably in a range between 40 gsm and 110 gsm, and most preferably in a range between 45 gsm and 90 gsm.

The barrier coating layer 6 can provide an improved water resistance at 25°C as well as provide a suitable grease resistance.

The packaging material 2 can be tightly sealed, e.g. by using adhesive(s), after the product to be packed has been placed in the package 1 . Alternatively or in addition to the adhesive(s), the packaging material 2 can be heat-sealable Heat sealability is determined at 0.6 bar sealing pressure, by using 1 .0 s dwell time. In an embodiment, the barrier coating layer 6 is heat sealable, at least, at 160°C (at 0.6 bar sealing pressure and 1 .0 s dwell time). The barrier coating layer 6 can further be heat sealable at 140°C. Moreover, the barrier coating layer 6 is preferably heat sealable at 120°C. In a preferred embodiment, the barrier coating layer 6 is heat sealable, at least, at temperatures from 120°C up to 160°C. Technical effect of the heat sealability is to provide, cost efficiently, good barrier properties over the sealing.

The packaging material 2 according to the invention is preferably made by a paper machine 10. The paper or paperboard 5 can be coated at a paper mill by using a coating unit 10 for applying the barrier coating 6 as shown in Fig. 3. The coating unit 10 can comprise one or more coating devices. The coating unit 10 can be a dispersion coating unit, such as size press, metering size press, rod coater, blade coater, curtain coater, foam coater, flexo coater, or gravure coater.

The package 1 can consist of the packaging material, or it can comprise some other materials in addition to the packaging material 2, for example in the form of a so-called “window”. However, even in such a case, the content of the packaging material 2 may be at least 50%, preferably at least 60%, or 70%, more preferably at least 80%, and most preferably at least 90% of the surface area of an outer layer of said package 1 .

Thanks to the novel packaging material 2, predetermined barrier properties can be obtained in an environmentally friendly way by using a barrier coating layer, which barrier coating layer can be capable of marine biodegradation.

Experimental tests

Comparative Example 1

Polymerization for poly(glycolide-co-D,L-lactide) polymer and polyglycolide homopolymer:

The polymerization yields copolymers and homopolymers with a known scope of properties.

A solvent mixture was prepared by mixing 171.91 g of dimethyl formamide (DMF) and 171.86 g of toluene. Glycolide (72.00 g, 620 mmol), meso-lactide (9.95 g, 69.0 mmol), PVP 10 kDa (3.8848 g), and n-butanol (0.1028 g, 1.39 mmol) were weighed into a reactor together with all except approximately 2 mL of the solvent mixture. 1 ,8-diazabicyclo[5.4.0]undec-7-ene (DBU, 3.1412 g, 20.6 mmol) was weighed in a separate vial with the remainder of the solvent. The reactor was stirred at room temperature with a mechanical stirrer at 250 rpm until the solution was visually homogenous. The same stirring speed and temperature were maintained throughout the whole reaction. The reaction was started by addition of the contents of the DBU vial into the reactor. The solution turned turbid immediately. The temperature of the reaction rose to 34.9 °C after approximately 5 minutes of reaction and after 10 minutes the temperature was measured to be 31.0 °C. After an hour (solution temperature 23.8 °C) the product was filtered from the solution using a sintered glass filter. The precipitate was washed with 1 :2 (vol.) mixture of DMF and toluene on the filter. The product was further washed three times with 300 mL of dichloromethane. Finally, the polymer was dried in a vacuum oven at room temperature.

Comparative example 2

Polymerization for poly(glycolide-co- s-caprolactone)

The polymerization yields copolymers with scope of properties not optimal for film formation in typical paper coating processes at paper machines.

Caprolactone (0.5475 g, 4.80 mmol), glycolide (5.0015 g, 43.1 mmol), ethylene glycol (0.0298 g, 0.480 mmol), and 10 mL of dimethyl formamide (DMF) were added into a flask. The flask was purged with nitrogen for 15 minutes and heated to 130 °C. Stannous octoate (0.5818 g, 1 .44 mmol) was dissolved in 2 mL of DMF and the solution was added into the heated reaction flask against nitrogen flow.

The reaction was allowed to proceed at 130 °C for 3 hours. Afterwards, the mixture was cooled to room temperature and the formed precipitate was washed thoroughly with ethanol. The product was dried under high vacuum at 30 °C overnight.

In the syntheses, which contained poly(vinyl pyrrolidone) (Mw 10 kDa), the polymer was added into the reaction mixture together with the monomers.

Example 1

Polymerization for poly(glycolide-co-D,L-lactide-co-£-caprolactone) terpolymers.

The polymerization yields terpolymers with properties beyond those produced by the methods describes in the comparative examples 1 and 2. Glycolide (2.9993 g, 25.8 mmol), meso-lactide (2.9806 g, 20.7 mmol), caprolactone (0.5930 g, 5.20 mmol), and ethylene glycol (0.0332 g, 0.535 mmol) were dissolved in 5 mL of DMF. The mixture was purged with nitrogen for 15 minutes. In a separate vial, tin(ll) 2-ethylhexanoate (0.6379 g, 1.57 mmol) was dissolved in 2 mL of DMF. The reaction flask was heated to 130 °C and the tin(ll) 2-ethylhexanoate solution was added into the solution against nitrogen flow. The reaction was allowed to proceed at 130 °C for 2 hours.

After cooling to room temperature, the polymer was isolated by precipitation to an excess of ethanol. The product was further purified by a second precipitation from CH2CI2 into diethyl ether. The product was dried in high vacuum at 30 °C.

Comparative example 3

Poly(glycolide-co-D,L-lactide) copolymers with varying lactic acid content were characterized to demonstrate thermal properties of these copolymers.

Composition and properties of poly(glycolide-co-D,L-lactide-) polymers prepared according to the previous Example are shown in Table 1 .

Table 1 . Parameters of poly(glycolide-co-D,L-lactide) polymers. On cooling, no crystallization was observed.

‘Prepared in acetonitrile; M/l - monomer/initiator; M _w - mass average molar mass; T _m - melting temperature; AHf - melting enthalpy; T _g - glass transition temperature; n.d. - not detected

Copolymerizing with D,L-lactide had very limited effect on thermal properties of the product. Measurements showed slightly decreasing melting temperature and clearly decreasing crystallinity with increased lactic acid content. However, even at 40 mol-% lactic acid content, the melting temperature remained as high as 180 °C, making the products unsuitable for realistic dispersion coating processes in paper making. The glass transition temperature of these copolymers remained in a range of 37-39 °C, regardless of the ratio of lactic and glycolic acid. Glass transition temperatures were clearly above ambient temperature, making the copolymers too rigid for barrier coatings in flexible packaging.

Comparative example 4

Poly(glycolide-co-£-caprolactone) copolymers with varying caprolactone content were characterized to demonstrate thermal properties of these copolymers.

The composition and properties of poly(glycolide-co-£-caprolactone) polymers prepared according to comparative example 2 is shown in Table 2.

Table 2. Parameters of poly-(glycolide-co-£-caprolactone)-polymers .

M/1 - monomer/initiator; M _n - number average molar mass; M _w - mass average molar mass; PDI - polydispersity index; T _m - melting temperature; AHf - melting enthalpy; T _g - glass transition temperature, n.a. not analyzed due to insolubility in solvent for NMR-analysis

Copolymerizing with caprolactone lowered the glass transition and melting temperatures compared to pure poly(glycolic acid) but was unable to produce a polymer with desired thermal properties. The melting points of produced poly(glycolide-co-£-caprolactone) batches remained high (>160°C) even at highest content of caproic acid (12-13 mol-%).

Example 2

Poly(glycolide-co-D,L-lactide-co-£-caprolactone) terpolymers with varying composition of the hydroxy acid units were characterized to demonstrate suitable compositions for polymers for water-based paper coating process conditions.

The composition and properties of poly(glycolide-co-D,L-lactide-co-£- caprolactone) polymers (terpolymers) prepared according to Example 1 are shown in Table 3.

Table 3. Compositions, molecular masses, and thermal properties of poly(glycolide-co-D,L-lactide-co-caprolactone) polymers.

*) In case of multiple melting phenomena, values for each melting peak are shown.

**) Melting temperature observed from powder in small aluminum dishes placed in an oven for 10 min at temperatures between 70 and 150 °C in 10 K intervals. The lowest temperature with powder fused to small droplets is announced as melting temperature. n.a. not analyzed. M _n - number average molar mass; M _w - mass average molar mass; PDI - polydispersity index; T _m - melting temperature; AHf - melting enthalpy; T _g - glass transition temperature.

Terpolymers with different compositions were synthesized, varying fractions of caprolactone and lactide in feed between 10-25%, and 5-40 mol-%, respectively. Glass transition temperature decreased with increasing caprolactone content in the polymer, dropping below 20 °C at 15%, and to 0-5 °C at 20% molar fraction of caproic acid units (10% = 20 C; 15% = 10 C; 20% = 5 C), making this composition very flexible at ambient temperature.

Melting behavior was highly dependent on polymer composition. Up to three melting peaks were observed by DSC:

- polycaprolactone rich fraction at approximately 50-60 °C

- terpolymer fraction at approximately 90-160 °C

- poly(glycolic acid) rich fraction at approximately 200 °C

Polymers 15, 16, 20, and 21 exhibited no melting and were thus fully amorphous. Polymers 17, 18 and 19 had distinct melting points for polycaprolactone and terpolymer fractions, the latter melting point being highly dependent on composition. In polymer 17 there was also a poly(glycolic acid) rich fraction. Terpolymer fraction dominated crystallinity in polymers 17 and 19, and in polymer 18 the fractions were equal.

Based on the results of Example 2 and Comparative Examples 3 and 4, when glycolic acid fraction in terpolymer decreased below 50 mol-%, the polymer became fully amorphous. Caprolactone amount was especially important for adjusting the melting point of terpolymer phase, which was clearly higher in polymer 19 than in 17 and 18. The presence of poly(glycolic acid) rich phase in polymer 17 suggested that a certain amount of lactic acid helps to prevent the formation of this high melting point fraction. The oven melting tests clearly showed that this crystalline phase, even as a minor fraction, significantly increased the film forming temperature. The ideal composition of the final polymer product should therefore be optimized according to following principles: i) 50-85 mol-%, or preferably 60-85 mol-% , or more preferably 65- 80 mol-% of glycolic acid, to facilitate crystallinity for mechanical integrity and barrier properties, ii) 5-30 mol-%, or preferably 9-25 mol-%, or more preferably 12-20 mol-% of caprolactone, to lower glass transition temperature and terpolymer phase melting point to a suitable level, and iii) 5-30 mol-%, or preferably 6-20 mol-%, or more preferably 8-18 mol-%, or even more preferably 10-15 mol-% of lactic acid, to prevent formation of large glycolic acid rich domains with high melting point.

Example 3

Barrier coating layer on a paper

Selected polymers were coated from solvent solution on base paper with a grammage of 55 g/m ² and 90 g/m ² . The coated sheets were dried at room temperature and conditioned before testing.

The coated papers were tested for water vapor transmission rate (WVTR ISO 2528 or modified ASTM F1249-13, 85% relative humidity and 23°C. Oxygen transmission rate at 50% relative humidity and 23°C was measured by modified ASTM F 1927-14.

Table 4. Barrier properties of paper coated with the poly(glycolide-co-D,L- lactide-co-£-caprolactone) polymer.

* ISO 2528; ** modified ASTM F1249-13

The measured barrier properties show that coatings have good water vapor barrier at elevated humidity and also a good oxygen barrier.

Example 4 Barrier properties of films

Films were prepared from selected polymers and barrier properties measured (Table 5). Water vapor transmission rate was measured by modified ASTM F1249-13 at 85% relative humidity and 23°C and oxygen transmission rate at 50% relative humidity and 23°C by modified ASTM F1927-14

Table 5. Properties of films from poly(glycolide-co-D,L-lactide-co-£- caprolactone).

Example 5

Preparation of aqueous dispersion

30 g of polymer and plasticizer (15 pph of polymer) were heated to 110°C. The mixture was stirred with an overhead-stirrer using an anchor-type of stirrer head in a round-bottom glass reactor at 110°C with a speed of 35 rpm for 10 min. Then, the temperature set point was dropped to 90°C. When 90°C was reached, aqueous polyvinyl alcohol (PVA) (Poval 40-88, 15 pph of polymer, 7% solids content) with ammonia (10 % of PVA solution) and Hepes buffer solution (1 % of PVA-solution) was added in seven steps at intervals of 10 min while stirring with 90 rpm at 90°C. After that, stirring was continued with 150 rpm for 15 min and then the heating was stopped.

Post treatment was done using Ultra turrax using 12000 rpm for 12 min.

Characteristics of a typically obtained aqueous dispersion were a solids content of 37 %, Brookfield viscosity of 400 cP at 100 rpm. The particle size was measured using laser diffraction, and the particle sizes (volume) were D90 < 1000 nm.

Example 6 Barrier coating layer on a paper

Coating of an aqueous dispersions according to example 5 was performed using an ERICHSEN sheet coater at 50 mm/s using grooved metering rods (40 - 80 pm) to adjust coat weight. Coated papers were dried in air circulating oven for 5 min with a temperature setting of 105°C. Coat weight was determined by drying in oven at 105°C for 1 h and subtracting dry weight of paper dried in a similar manner. Coating thickness was determined as a difference in thickness between coated and uncoated papers. Oxygen transmission rate at 50% relative humidity and 23°C was measured by modified ASTM F1927-14. The base paper had oxygen transmission rate of » 2000 cm ³ /(m ² ,d).

Table 4. Barrier properties of 90 gsm base paper coated with an aqueous dispersion of poly(glycolide-co-D,L-lactide-co-£-caprolactone) polymer (polymerization conditions according to batch 18).

Surprisingly, thanks to the novel solution, dispersible coating capable of forming a barrier layer having good barrier properties as well as low tackiness level was provided. Thus, thanks to the novel solution, it was possible to produce a packaging material having predetermined grease repellence, predetermined water vapor and oxygen barrier, as well as sufficient mineral oil barrier. Thus, thanks to the novel solution, it was possible to obtain a packaging material having improved barrier coating comprising polymeric material which can be biodegradable even in marine environments.

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.