EP4735255A1

EP4735255A1 - Pha multilayer extrusion coating

Info

Publication number: EP4735255A1
Application number: EP24831154.0A
Authority: EP
Inventors: Gisela CUNHA; Ebrahim SHOKRI; Kaj Backfolk; Åsa NYFLÖTT
Original assignee: Stora Enso Oyj
Current assignee: Stora Enso Oyj
Priority date: 2023-06-27
Filing date: 2024-06-11
Publication date: 2026-05-06
Also published as: SE2330297A1; AU2024309120A1; SE547091C2; WO2025003815A1

Abstract

A multilayer coated laminate (1) comprising a substrate (2) with a first side (2a) and a second side (2b). The laminate further comprises a co-extrusion coated tie 5 layer (3) which is coated on first side (2a) of the substrate, wherein the tie layer comprising PVAc and/or PBSA, which tie layer has a thickness of 1-10 µm, preferably 2-7 µm; and a PHA layer (4), preferably PHBH, which is co-extrusion coated on the tie layer, the PHA 10 layer has a thickness of 5-25 µm, preferably 10-15 µm.

Description

PHA MULTILAYER EXTRUSION COATING

TECHNICAL FIELD

The present invention relates to a multilayer coated laminate comprising a substrate with a first side and a second side in accordance with the main claims 1 , 2 and 4 .

BACKGROUND - PROBLEM

Renewable and sustainable alternatives to fossil-based or plastic packaging are sought after, and fibre-based materials offer a promising solution . Fibre-based substrates , such as paper or paperboard, are commonly coated or laminated with thin polymer layers through extrusion or dispersion processes . These multi-layered structures enhance the materials ' barrier properties , including sealing and resistance to various factors . In some cases , aluminium foil has been incorporated into laminates to provide additional barriers against factors like aroma , light , water vapor , and gases .

However, conventional polymers used in such applications are fossil-based, and both these polymers and aluminium foil are not environmentally sustainable . Consequently, their appeal is diminished, particularly when considering home or industrial recycling and composting .

Bio-based polymers hold promise as potential replacements for conventional polymers in this field, although their availability remains limited . Some bio-based polymers still present notable processing challenges due to their unique characteristics , unique molecular structure and early stages of development . Polyhydroxyalkanoates ( PHA) are a class of bio-based polymers , which is both recyclable and compostable , that show great potential for the packaging sector . PHAs exhibit a wide range of properties depending on the monomers incorporated into their structures .

However, there are hurdles associated with PHAs , including their inherent sensitivity to heat , as they can decompose easily at temperatures exceeding 175 ° C or even lower . Additionally, in the specific case of extrusion coating, challenges arise regarding necking and adhesion to paperboard . Therefore , achieving the right PHA formulation and implementing appropriate processing conditions are crucial factors . Furthermore , the sequence in which different layers are deposited onto the paperboard plays a significant role in the overall effectiveness of the packaging solution .

OBJECT OF THE INVENTION

An obj ective of this invention is to enhance the processability of PHAs , enabling their use as superior environmentally friendly and sustainable alternatives to traditional polymers such as PE , PET and EVOH in multilayer fibre-based materials . The improved processability of PHAs will not compromise the barrier properties , mechanical strength, adhesion, and sealability performance of the multilayer material .

Therefore , there is a demand for a reliable technique to apply a PHA coating onto paperboard using extrusion, which : - Provides good processability, especially concerning necking and film forming ability and homogeneity.

- Provides a coating of less than 10 pinholes/m², preferably less than 5 pinholes/m², and most preferred 0- 2 pinholes/m² according to Standard EN 13676:2002.

- Provides a good liquid resistance of the ensuing material (COBB600 value <30 g/m², preferably <25 g/m², more preferred <20 g/m², and most preferred <18 g/m² according to standard method SCAN-P 12:64) .

- Ensuing material has good WVTR (WVTR 0.5-20 g/m²/day, preferably 7-15 g/m²/day measured at 23 °C and 50% RH according to ASTM F1249-20)

- Ensuing material has good grease barrier. Wherein the KIT >8, preferably KIT >10 and most preferred KIT =12 according to TAPPI standard T 559.

- Ensuing material has good crack resistance against negative and positive folding, i.e. good adhesion to the paperboard, but at the same time optimal adhesion so that the coated material is re-pulpable.

- Ensuing material is re-pulpable and recyclable according to PTS RH 021/97 test method for Category II products standard (PTS reject <20% and preferably <15%)

- Provides good sealability of the ensuing material

- Ensuing material has a bending resistance in MD (Machine Direction) of at least 120mN, such as in the in the range of 120-300 mN, preferably in the range 120-200 mN and most preferred 120-180 mN. Preferably the bending resistance in MD is at least 130 mN, such as in the range of 130-300 mN, preferably in the range

130-200 mN and most preferred 130-180 mN, according to ISO 2493-1.

- Ensuing material has a bending resistance in CD (crossmachine direction) of at least 50 mN, such as in the range 50-200 mN, preferably 50-150 mN and most preferred 50- 90 mN . Preferably the bending resistance in CD is at least 55 mN, such as in the range 55 -200 mN, preferably 55-150 mN and most preferred 55-90 mN, according to ISO 2493-1 .

- Ensuing material is home and industrially compostable according to at least one of EN 13432 : 2000 , ASTM D6868 -21 or/and AS-4736-2006 .

SUMMARY OF THE INVENTION

In a first aspect of the invention the laminate is characterized in that the laminate further comprises :

- a co-extrusion coated tie layer which is coated on first side of the substrate , wherein the tie layer comprising PVAc and/or PBSA, which tie layer has a thickness of 1-10 pm, preferably 2-7 pm; and

- a PHA layer, preferably PHBH , which is co-extrusion coated on the tie layer , the PHA layer has a thickness of 5 -25 pm, preferably 10-15 pm . (Claim 1 )

In a second aspect of the invention the laminate is characterized in that the laminate further comprises :

- an extrusion coated adhesion layer , which is coated on the first side of the substrate , wherein the adhesion layer is a compound comprising PHA, preferably PHBH , and an additive of PVAc and/or PBSA; and

- an extrusion coated PHA layer, preferably PHBH , which is coated on the adhesion layer . (Claim 2 )

In a third aspect of the invention, the laminate is characterized in that the laminate further comprises :

- an extrusion coated adhesion layer , which adhesion layer is coated on the first side of the substrate , wherein the adhesion layer is a compound comprising PHA, preferably PHBH , and an additive of PVAc and/or PBSA; and - an extrusion coated sealability layer which is coated on the adhesion layer, wherein the sealability layer comprising PHA, preferably PHBH, and an additive of PVAc and/or PBSA. (Claim 4 )

DEFINITIONS

Polyhydroxyalkanoate ( PHA)

PHAs or polyhydroxyalkanoates shall in the context of the patent application refer to a biopolyester family that has a variety of structures and that are synthesized by a broad range of natural and genetically engineered bacteria and genetically engineered plant crops . PHAs can be synthesized in a wide range of environmental conditions and media by 30% of bacteria that live in soil . The bacteria produce PHAs by fermentation of sugar or lipids with the aim to store carbon and energy . Examples of bacterial strains that can produce PHAs include Alcaligenes eutrophus , Alcaligenes latus , Azotobacter , Aeromonas , Comamonas , Pseudomonads , and other genetically engineered organisms , such as genetically engineered microbes like Pseudomonas , Ralstonia and Escherichia coll . In general , PHAs are formed by enzymatic polymerization of one or more monomer units inside living bacteria or plant cell . Over 100 different types of monomers have been identified and incorporated into the PHA polymers , including 3-hydroxybutanoic acid and 3-hydroxypentanoic acid . PHAs can be classified into homopolymers , such as the well-known polyhydroxybutyrate ( PHB ) , or co-polymers like poly ( 3-hydroxybutyrate-co-3-hydroxyvalerate ) ( PHBV) . Additionally, depending on the size of the carbon chain, they are further categorized into short chain length ( SCL ) , medium chain length (MCL ) or long chain length (LCL ) PHAs . Since they constitute a broad family of biodegradable polymers , PHAs display very versatile properties that can benefit many different industrial applications , including cosmetics , biomedicine and packaging , to name a few .

PBSA

Poly (butylene succinate-co-butylene adipate ) ( PBSA) is a biodegradable , semi-crystalline polyester produced by cocondensation of succinic and adipate acid with 1-4 - butanediol . All three building blocks can be produced either from renewable feedstock such as glucose and sucrose via fermentation or from petroleum-based feedstock .

PVAc

Polyvinyl acetate ( PVAc ) is a polymer obtained for example through polymerizing the vinyl acetate monomer , which can be made through catalytic oxidative addition of acetic acid to ethylene . All building blocks can be obtained from either petroleum or bio-based feedstock . The polymer can be further modified to contain for example carboxyl groups , or dibutyl maleate groups .

FIGURES

In the following description, the invention will be described further with reference to Figures 1-6 . Note that the drawings in Figures 1-6 are schematical and not to scale .

Figure 1 discloses a co-extruded embodiment of the invention . Figure 2 -5 discloses compounding embodiments of the invention .

Figure 6 discloses an embodiment comprising co-extrusion and compounding .

DESCRIPTION OF THE INVENTION

It has surprisingly been discovered that the addition of a minor quantity of polyvinyl acetate ( PVAc ) or a suitable polysaccharide significantly enhances the processability of PHA, especially in terms of necking . Notably, the preferred range for PVAc concentration is between 2-20 wt% , preferably 5 -15 wt% . Furthermore , it was observed with great surprise that this addition also enhances the adhesion between PHA and the paperboard substrate . The adhesion strength is quantified using a straightforward cross-cut peel-off test method .

The mentioned polysaccharide above is preferably long chain cellulose esters with a chain length of fatty substituents bc6 ( cellulose hexanoate esters ) . Alternatively, shorter chain length cellulose acetate ( CA) , cellulose acetate propionate ( CAP ) , and cellulose acetate butyrate ( CAB ) can be used . These esters can also be blended to make adj ust necking , barrier properties and processability . The preferred amounts are 2-20 wt% and more preferred 2-15 wt% .

The adhesion between PHA and the paperboard substrate can be further enhanced by incorporating a small quantity of poly (butylene succinate-co-adipate ) ( PBSA) or other polymers , including biopolymers . This can be achieved through co-extrusion or compounding methods with PHA. In the case of co-extrusion, the optimal thickness for the PBSA layer ranges from 3-10 pm, with a preferred range of 4-8 pm, while the PHA layer thickness is preferred to be between 5-25 pm, with an ideal range of 10-15 pm. For the compounding case, the recommended amount of PBSA to be added is between 5-25 wt% . For the PHA+PBSA compound 2-10 wt% of PVAc can be added.

Notably, the incorporation of PVAc and/or PBSA into the PHA compound surprisingly enhances the sealability properties as well .

A preferred PVAc for this invention exhibits a glass transition temperature (Tg) ranging from 30-60 °C, and preferably a Tg within the range of 40-50°C (evaluated using DSC according to DIN EN ISO 11357-2) .

Additionally, the preferred melt flow rate (MFR) of PVAc falls between 5-20 cm³/10 min, and most preferred between 5-10 cm³/10 min (measured at 150 °C/2.16 Kg/2 mm according to ISO 1133) . The softening point of PVAc is within the range of 100-140 °C, with a preferred range of 110-125 °C (determined using the Ring and Ball method according to DIN ISO 4625) . The molecular weight (Mw) of PVAc is between 120k-140k g/mol, preferably in the range of 125k-135k g/mol (measured using SEC with a PS- standard) .

The preferred PBSA for this invention has a melting temperature (Tm) within the range of 80-120 °C, preferably within the range of 85-115 °C. The melt flow rate (MFR) of PBSA is preferably between 5-20 g/10 min and most preferred for 10-15 g/10 min (measured at 190 °C/2.16 Kg according to ISO 1133) . The glass transition temperature (Tg) of PBSA is within the range of -50 to - 10 °C, preferably within -45 to -20 °C (determined using DSC according to DIN EN ISO 11357-2) .

The preferred PHA is a medium chain length (MCL) PHA with a melt flow index within the range of 3-12 g/10 min, preferably within the range of 4-10 g/10 min, and most preferred within the range 4-8 g/10 min. The melting temperature of the preferred PHA falls within the range of 100-170 °C, preferably within the range 110-165 °C, and most preferred within 130-160 °C.

The use of different types of PHAs possessing different properties also makes an impact in the processability, adhesion and sealability properties. Another important factor is the order of deposition of the different PHA- based layers .

If using more than one PHA, the second type of PHA may be a pure or compound MCL or short chain length (SCL) PHA and its melt flow index should be compatible with the first PHA type and its melting temperature should be in the range 130-190 °C, preferably 140-180 °C and most preferred 150-170 °C.

Pure SCL can also be used with a melt flow index in the range 3-12 g/10 min, preferably 4-10 g/10 min and most preferred 5-8 g/10 min. The melting temperature for the pure SCL is in the range 140-200 °C, preferably 150-190 °C and most preferred 160-180 °C. Figure 1 discloses a first embodiment of the invention, wherein a multilayer coated laminate 1 comprises a substrate 2 with a first side 2a and a second side 2b . The laminate 1 further comprises a co-extrusion coated tie layer 3 which is coated on the first side 2a of the substrate . The tie layer 3 comprising PVAc and/or PBSA and has an average thickness of 1-10 pm, preferably 2-7 pm. The tie layer 3 has a coat weight in the range 2-12 gsm, preferably 4-12 gsm. The tie layer 3 is designed to ensure good adhesion to sealing or barrier layer . When using the PBSA as a tie layer to improve adhesion, the preferred PBSA content in the tie layer is at least 50 wt% and preferably at least 75 wt% such as 85 -100 wt% . The laminate further comprises a PHA layer 4 which is coextruded on the tie layer 3 . The PHA layer has a thickness of 5-25 pm, preferably 10-15 pm .

Figure 2 discloses a second embodiment of the invention, wherein a multilayer coated laminate 1 comprises a substrate 2 with a first side 2a and a second side 2b . The laminate further comprises an extrusion coated adhesion layer 5 , which is coated on the first side 2a of the substrate 2 . The adhesion layer 5 is a compound comprising PHA, preferably PHBH, and an additive of PVAc and/or PBSA. The amount of additives in the adhesion layer are 5-35 wt% of the total amount , if only PBSA is used the amount is 5-25 wt% . The adhesion layer 5 has a PHA content above 50 wt% , preferably above 75 wt% . The adhesion layer 5 has a thickness of 1-10 pm, preferably 2 -7 pm. The adhesion layer 5 has a coat weight in the range 2-12 gsm, preferably 4 -12 gsm. The laminate further comprises an extrusion coated PHA layer 4 , preferably PHBH , which is coated on the adhesion layer 5 . Figure 3 discloses a third embodiment of the invention, wherein the second side 2b, of the laminate in figure 2 , is coated with an extrusion coated processability layer 7 , which processability layer ( 7 ) comprising PHA, preferably PHBH , and PVAc . The processability comprises 2 -20 wt% PVAc, preferably 5-15 wt% PVAc . The coat weight of the processability layer is 2-25 gsm, preferably 5-25 gsm . The processability layer 7 is designed to prevent necking and to the substrate 2 . The processability layer is a layer with PHA with mentioned additives , preferably without any fillers . The PHA in the processability layer 7 may be a mixture of at least two different PHA grades such as PHBH and PHBV .

Figure 4 discloses a fourth embodiment of the invention, wherein a multilayer coated laminate 1 comprises a substrate 2 with a first side 2a and a second side 2b . The laminate further comprises an extrusion coated adhesion layer 5 , which adhesion layer 5 is coated on the first side 2a of the substrate . The adhesion layer 5 is a compound comprising PHA, preferably PHBH, and an additive of PVAc and/or PBSA . The laminate finally comprises an extrusion coated sealability layer 6 which is coated on the adhesion layer 5 , wherein the sealability layer 6 comprising PHA, and an additive of PVAc and/or PBSA . The sealability layer 6 has a coat weight in the range 5-40 gsm . The additives of PVAc and/or PBSA improves the sealability . The sealability layer 6 is designed to ensure good heat sealability or sealability when using e . g . , ultrasound or high focused ultrasound technology . The sealability layer also provide a good or high barrier for food with low or high pH ( 1-12 ) . Figure 5 discloses a fifth embodiment of the invention, wherein the second side 2b of the laminate in figure 1 , is extrusion coated with a processability layer 7 , which processability layer 7 comprising PHA, preferably PHBH , and PVAc .

Figure 6 discloses a sixth embodiment of the invention, wherein the second side 2b of the laminate in figure 3 , is extrusion coated with a processability layer 7 , which processability layer 7 comprising PHA, preferably PHBH , and PVAc .

Processing conditions

In accordance with the invention, the processing conditions for the chill roll in extrusion machine should be as follows :

The temperature of the chill roll plays a crucial role as it significantly influences the optimal crystallization of PHA. It is recommended to maintain the chill roll temperature within the range of 20-90 ° C . Ideally, the temperature should fall between 30-80 ° C, with the most preferred range being 40-70 ° C .

Depending on the desired coating finish, the chill roll can be either smooth, providing a glossy coating , or micro-patterned, resulting in a matte coating .

The screw speed should be maintained within the range of 30-180 rpm, preferably 50-170 rpm, and most preferred 70-150 rpm. The air gap between the die and chill roll should be in the range 110-180 mm, preferably 120-165 mm, and most preferred 130-150 mm.

Substrate

The substrate 2 , to be extruded, in this invention is ideally a multiple-layered paper or paperboard, specifically suited for applications in packaging various items . Examples of suitable substrates include packaging paper, paperboard, and containerboard . Among these options , a particularly preferred substrate is multiply paperboard and/or containerboard specifically designed for single-use packages intended for food or beverages . This substrate is well-suited for packaging items such as frozen food, chilled food, cold beverages , hot drinks , and even fish, ensuring their quality and freshness .

The substrate comprises one or more middle plies which offer the advantageous attribute of providing bulk . This middle ply comprises a combination of sulphate/ kraf t pulp and chemi-thermomechanical pulp ( CTMP ) . The pulp used can be either unbleached or bleached . The middle ply can be composed of fibres derived from chemi-thermomechanical pulp (CTMP ) , High temperature CTMP ( HT-CTMP ) or thermomechanical pulp ( TMP ) . Preferably, the middle ply comprises a mixture of sulphate pulp and CTMP or sulphate pulp , broke and CTMP . The top and back plies preferably comprise of sulphate pulp . It is preferred that the top and back plies do not contain CTMP fibres . The first side of the paperboard is designed to be the print side , while the second side is intended to become the interior of the resulting packaging. The substrate utilized may include up to 20 wt% recycled fibers as part of its composition.

The substrate, to be extruded, might contain a surface planarization layer to enhance its properties . This surface planarization layer comprises materials such as nanocellulose, nanocrystalline cellulose, microf ibrillated cellulose, starch, starch-pigment, or fines collected from pulp fractionation. The amount of the applied surface planarization layer is within the range of 1.5 to 10 grams per square meter (gsm) , preferably in the range of 3 to 8 gsm. To further enhance the performance of the coated surface, the planarization layer contains a resin component in the range of 0.5 to 30 weight percent (wt%) . Examples of suitable resins include AKD, ASA, PVAc latex or Rosin resin. The inclusion of such resin improves barrier properties and raw edge penetration.

The substrate, or at least two plies, is preferably free from wet strength resin.

Example of preferred paperboard for the substrate exhibits specific characteristics. The base board has a desirable grammage of over 150 grams per square meter (gsm) , ensuring its robustness. Additionally, the substrate's L&W (15°) bending resistance must meet or exceed 145 mN in the machine direction (MD) according to the ISO 2493-1 standard. These specifications ensure the substrate's structural integrity and performance. At least one ply has a density below 600 kg/m³, preferably below 550 kg/m³ and most preferred in the range 200-500 kg/m³, according to ISO 534:2011. Physical properties of the multilayered laminate

The innovative multilayer coated laminate may exhibit a water absorption rate that is below 25 g/m² , preferably less below 20 g/m² and most preferred below 15 g/m² . This measurement is conducted using COBB600 in accordance with SCAN-P 12 : 64 .

The coated side of the laminate has a water vapor transmission rate (WVTR) , measured at 23 ° C and 50 % relative humidity ( RH ) , below 25 g/m²/day, preferably below 20 g/m²/day, and most preferred below 10 g/m²/day, according to ASTM F1249-20 .

The laminate can be effectively recycled into same or similar or other paper products using standard repulping technology . During the repulping process , the cellulose fibers are separated and can be recycled after being cleaned . The remaining fraction that cannot be repulped is known as "rej ects" which can consist of agglomerated fibers and other solid foreign materials . These rej ects need to be removed for disposal or burning .

In preferred embodiments , the percentage of rej ects obtained from repulping the packaging material is less than 20 wt% , preferably less than 15 wt% , more preferred less than 10 wt% and most preferred less than 5 wt% , based on a dry weight of 100 wt% of the packaging material . The determination of rej ects is conducted using the PTS test method RH021 / 97 by category II . The laminate thus may be referred to as a repulpable and recyclable packaging material .

The laminate for packaging is designed to be highly suitable for containing liquids , greasy food, dry food, chilled food and/or frozen food . In certain embodiments , the packaging takes the form of a beverage container, specifically a cup or a tray . It can also be utilized as a disposable drinking cup , clamshell , or other disposable items . A notable advantage of the laminate is that it does not contain a metal layer , such as aluminum foil , making it an excellent option for biodegradable and/or compostable applications .

In the foregoing, the invention has been described on some specific embodiments . However, a skilled person realises that other embodiments and variants are possible within the scope of the following claims . For example , the PHA or parts of the PHA that is used in the embodiments may be recycled PHA.

Claims

C L A I M S

1. A multilayer coated laminate (1) comprising a substrate (2) with a first side (2a) and a second side (2b) , characterized in that the laminate further comprises :

- a co-extrusion coated tie layer (3) which is coated on first side (2a) of the substrate, wherein the tie layer comprising PVAc and/or PBSA, which tie layer has a thickness of 1-10 pm, preferably 2-7 pm; and

- a PHA layer (4) , preferably PHBH, which is co-extrusion coated on the tie layer, the PHA layer has a thickness of 5-25 pm, preferably 10-15 pm.

2. A multilayer coated laminate (1) comprising a substrate (2) with a first side (2a) and a second side (2b) , characterized in that the laminate further comprises :

- an extrusion coated adhesion layer (5) , which is coated on the first side (2a) of the substrate, wherein the adhesion layer (5) is a compound comprising PHA, preferably PHBH, and an additive of PVAc and/or PBSA; and

- an extrusion coated PHA layer (4) , preferably PHBH, which is coated on the adhesion layer (5) .

3. Laminate according to claim 2, wherein the second side (2b) of the substrate (2) is coated with an extrusion coated processability layer (7) , which processability layer (7) comprising PHA, preferably PHBH, and PVAc.

4. A multilayer coated laminate (1) comprising a substrate with a first side (2a) and a second side (2b) , characterized in that the laminate further comprises:

- an extrusion coated adhesion layer (5) , which adhesion layer (5) is coated on the first side (2a) of the substrate, wherein the adhesion layer (5) is a compound comprising PHA, preferably PHBH, and an additive of PVAc and/or PBSA; and

- an extrusion coated sealability layer (6) which is coated on the adhesion layer (5) , wherein the sealability layer comprising PHA, preferably PHBH, and an additive of PVAc and/or PBSA.

5. Laminate according to claim 1 or claim 4, wherein the second side (2b) of the substrate (2) is extrusion coated with a processability layer (7) , which processability layer (7) comprising PHA, preferably PHBH, and PVAc.

6. Laminate according to any of above claims, wherein the glass transition temperature (Tg) for PVAc ranging from 30-60 °C, preferably within the range of 40-50°C.

7. Laminate according to any of above claims, wherein the glass transition temperature (Tg) for PBSA ranging from -50 °C to -10 °C, preferably within the range of -45 °C to -20 °C.

8. Laminate according to any of above claims, wherein the PHA is a medium chain length (MCL) PHA with a melt flow index in the range 3-12 g/10 min, preferably 4-10 g/10 min and most preferred 4-8 g/10 min, and having a melting temperature in the range 100-170 °C, preferably 110-165 °C and most preferred 130-160 °C.

9. Laminate according to any of above claims, wherein the amount of added PBSA to the adhesion layer (5) is 5-25 wt% .

10. Laminate according to preceding claim 9, wherein the amount of PVAc to the PHA and PBSA compound in the adhesion layer (5) is 2-10 wt% .

11. Laminate according to any one of above claims, wherein the substrate (2) is a multi-layered paper or paperboard .

12. Laminate according to any one of above claims, wherein the substrate (2) comprises one or more bulky middle ply which offer the advantageous attribute of providing bulk.

13. Laminate according to claim 12, wherein the middle ply comprises a combination of sulphate/kraf t pulp and chemi-thermomechanical pulp (CTMP) .

14. Laminate according to any of claims 12-13, wherein the top ply and the back ply of the substrate comprise sulphate pulp and preferably less than 10 wt% CTMP.

15. Laminate according to any of claims 11-14, wherein the substrate comprises up to 20 wt% of recycled fibres as part of its composition.

16. Laminate according to any of preceding claims, wherein the substrate (2) is a base board with a grammage over 150 gsm.

17. Laminate according to any of preceding claims, wherein the L&W (15°) bending resistance of the substrate exceed 145 mN in the machine direction (MD) according to ISO 2493-1.

18. Laminate according to any preceding claims, wherein the substrate (2) comprising a surface planarization layer .

19. Laminate according to claim 18, wherein the planarization layer comprises materials such as nanocellulose, nanocrystalline cellulose, microf ibrillated cellulose, starch, starch-pigment or fines collected from pulp fractionation.

20. Laminate according to any of claims 18-19, wherein the amount of the applied surface planarization layer is within the range of 1.5 to 10 grams per square meter (gsm) , preferably in the range of 3 to 8 gsm.

21. Laminate according to any of claims 18-20, wherein the planarization layer comprises an amount of resin component, such as AKD, ASA or Rosin, in the range of 0.5 to 30 wt%.