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EP-4735255-A1 - PHA MULTILAYER EXTRUSION COATING

EP4735255A1EP 4735255 A1EP4735255 A1EP 4735255A1EP-4735255-A1

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.

Inventors

  • CUNHA, Gisela
  • SHOKRI, Ebrahim
  • BACKFOLK, KAJ
  • NYFLÖTT, Åsa

Assignees

  • Stora Enso Oyj

Dates

Publication Date
20260506
Application Date
20240611

Claims (20)

  1. 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. 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. 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. 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. 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. 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. 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. 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. 9. Laminate according to any of above claims, wherein the amount of added PBSA to the adhesion layer (5) is 5-25 wt% .
  10. 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. 11. Laminate according to any one of above claims, wherein the substrate (2) is a multi-layered paper or paperboard .
  12. 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. 13. Laminate according to claim 12, wherein the middle ply comprises a combination of sulphate/kraf t pulp and chemi-thermomechanical pulp (CTMP) .
  14. 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. 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. 16. Laminate according to any of preceding claims, wherein the substrate (2) is a base board with a grammage over 150 gsm.
  17. 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. 18. Laminate according to any preceding claims, wherein the substrate (2) comprising a surface planarization layer .
  19. 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. 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.

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 comp