Re-pulpable packaging material

Abstract

The invention relates to a packaging material comprising: a paperboard substrate comprising a first and a second side, at least one barrier layer applied on the first side of the substrate, the barrier layer comprising a water-soluble polymer selected from the group of polyvinyl alcohol, a copolymer of ethylene and polyvinyl alcohol, starch, carboxymethylcellulose and combinations thereof in an amount of at least 50 weight %, based on the dry weight of the barrier layer, an extrusion coated layer of a polyolefin on the barrier layer, and at least one dispersion barrier layer applied on the second side of the substrate, which at least one dispersion barrier layer forms a printing surface of the packaging material. The invention further relates to a method of manufacturing a respective packaging material.

Claims

1. A packaging material comprising: a paperboard substrate comprising a first and a second side, at least one barrier layer applied on the first side of the substrate, the barrier layer comprising a water-soluble polymer selected from a group consisting of polyvinyl alcohol, a copolymer of ethylene and polyvinyl alcohol, starch, carboxymethylcellulose, and combinations thereof in an amount of at least 50 weight %, based on a dry weight of the at least one barrier layer, an extrusion coated layer of a polyolefin on the at least one barrier layer, and at least one dispersion barrier layer applied on the second side of the substrate, wherein the at least one dispersion barrier layer forms a printing surface of the packaging material.

2. The packaging material according to claim 1, wherein the polyolefin of the extrusion coated layer is selected from a group consisting of polyethylene and polypropylene.

3. The packaging material according to claim 1, wherein the at least one barrier layer comprises the water-soluble polymer in an amount in a range of ≥50 weight % to ≤100 weight %, based on the dry weight of the at least one barrier layer.

4. The packaging material according to claim 1, wherein the water-soluble polymer of the at least one barrier layer is polyvinyl alcohol or a copolymer of ethylene and polyvinyl alcohol, and a grammage is in a range from ≥2 g/m.sup.2 to ≤7 g/m.sup.2.

5. The packaging material according to claim 1, wherein the water-soluble polymer of the at least one barrier layer is starch, and a grammage is in a range from ≥2 g/m.sup.2 to ≤10 g/m.sup.2.

6. The packaging material according to claim 1, wherein the water-soluble polymer of the at least one barrier layer is carboxymethylcellulose, and a grammage is in a range from ≥4 g/m.sup.2 to ≤6 g/m.sup.2.

7. The packaging material according to claim 1, wherein the at least one dispersion barrier layer comprises latex in an amount in a range of ≥40 weight % to ≤100 weight %, and a pigment in an amount in a range of ≥0 weight % to ≤60 weight %, the percentages being based on a dry weight of the at least one dispersion barrier layer of 100 weight %.

8. The packaging material according to claim 1, wherein the at least one dispersion barrier layer comprises starch and at least one hydrophobic polymer selected from a group consisting of: wax, styrene maleic anhydride (SMA), alkyl ketene dimers (AKDs), and a copolymer of ethylene and polyvinyl alcohol.

9. The packaging material according to claim 1, wherein the packaging material exhibits an oxygen transfer rate (OTR) below 5 cc/m.sup.2*day*atm, measured according to ASTM D3985, 23° C., 50% relative humidity (RH); or a water vapor transfer rate (WVTR) of below 10 g/m.sup.2 per day, measured according to ASTM F1249; or a water absorption rate of below 1 g/m.sup.2, as measured using COBB 1800, or any combination of the foregoing.

10. The packaging material according to claim 1, wherein reject received from a repulping of the packaging material is less than 15 weight %, based on a dry weight of the packaging material of 100 weight %.

11. A method of manufacturing the packaging material according to any claim 1, the method comprising the steps of: providing the paperboard substrate comprising the first and the second side, applying the at least one barrier layer on the first side of the substrate, applying the layer of the polyolefin on the barrier layer, and applying the at least one dispersion barrier layer on the second side of the substrate, wherein the layer of polyolefin is applied by extrusion coating using a chill roll, wherein a chill roll temperature is in a range of ≥10° C. to ≤25° C.

12. The method according to claim 11, wherein the polyolefin is selected from a group consisting of polyethylene and polypropylene, and wherein a extrusion of the polyethylene is performed at a melt temperature in a range of ≥300° C. to ≤330° C., or an extrusion of the polypropylene is performed at a melt temperature in a range of ≥295° C. to ≤320° C.

13. The method according to claim 11, further comprising: treating the paperboard substrate by corona treatment or flame treatment before being extrusion coated with the layer of polyolefin.

14. The method according to claim 11, further comprising: ozone treating the layer of polyolefin at the extrusion step.

15. A packaging comprising or being made from the packaging material according to claim 1.

Description

(1) Further features of the present invention will become apparent from the examples and figures, wherein:

(2) FIG. 1 is a schematic drawing of a packaging material according to an embodiment of the invention.

(3) FIG. 2 is a schematic drawing of a packaging material according to a further embodiment of the invention.

(4) The packaging material shown in FIG. 1 comprises a paperboard substrate 1. The paperboard substrate 1 has a first and a second side, wherein on the first side of the paperboard is coated with a barrier layer 3, wherein the barrier layer 3 comprises a water-soluble polymer selected from the group of PVOH, a copolymer of ethylene and PVOH, starch, carboxymethylcellulose and combinations thereof in an amount of at least 50 weight %, based on the dry weight of the barrier layer 3. A layer of polyolefin 4, such as of polyethylene or polypropylene, is extrusion coated on the barrier layer 3. The extrusion coated layer 4 will be in contact with the content of a packaging formed from the packaging material. The second side of the paperboard substrate 1 is coated with a dispersion barrier layer 4, wherein the dispersion barrier layer 4 forms the printing surface of the packaging material. The paperboard as shown in FIG. 1 is particularly suitable for heat-sealed packages for liquid and/or frozen food.

(5) The packaging material shown in FIG. 2 comprises a paperboard substrate 1, comprising three plies, a top ply 1a, a middle ply 1b and a back ply 1c. The middle layer 1b contains CTMP and sulphate/kraft pulp in order to give bulk. The pulp can be unbleached or bleached. The surface layer of the board 1a and 1c can contain surface sizer. On the second of side paperboard substrate, the top ply 1a is coated with a first dispersion barrier layer 2a, and a second dispersion barrier layer 2b is arranged on the first barrier layer 2a. The dispersion barrier layers are brought by dispersion barrier coating onto the paperboard substrate. The packaging material may be printed directly on the outermost dispersion barrier layer 2b. On the first side, the back ply 1c of the paperboard substrate is coated with a barrier layer 3, wherein the barrier layer 3 comprises a water-soluble polymer selected from the group of PVOH, a copolymer of ethylene and PVOH, starch, carboxymethylcellulose and combinations thereof in an amount of at least 50 weight %, based on the dry weight of the barrier layer 3. A layer of polyolefin 4, such as of polyethylene or polypropylene, is extrusion coated on the barrier layer 3. The extrusion coated layer 4 will be in contact with the content of a packaging formed from the packaging material.

EXAMPLE 1

(6) In order to evaluate the barrier properties of the packaging material of the invention, a test series was performed in which the barrier properties of packaging material manufactured in accordance with the invention was evaluated in a pilot trial using jet and rod coating.

(7) The paperboard substrate used in the test series was a baseboard of grammages between 190-232 gsm, which is a multi-layer paperboard with two outer layers made of bleached kraft pulps and a middle layer comprising bleached kraft pulp and CTMP.

(8) The paperboard substrates were coated with polyvinyl alcohol (PVOH) or starch forming a barrier layer on the reverse side, i.e. the side to form the inside of the thereof made package. The starch was a potato starch comprising at least 99 wt % of amylopectin. Thereafter the coated substrates were extrusion coated with polyethylene (PE) or polypropylene (PP) forming an extrusion coated layer. The extrusion coating was performed at a polymer melt temperature of around 300° C., further using a chill roll held at a temperature of 15-20° C. All samples were corona treated before the extrusion coating step.

(9) The samples were thus prepared to show the following coating structure:

(10) Baseboard/Barrier layer/Extrusion coated layer

(11) As a reference, a baseboard was extrusion coated with polyethylene without being pre-coated with a barrier layer (REF).

(12) Table 1 shows the grammage of the baseboard and the type and amount of applied barrier layer and extrusion coated layer.

(13) TABLE-US-00001 TABLE 1 Barrier Ext. coated Baseboard layer Extrusion layer grammage Barrier grammage coated grammage Test Point [g/m.sup.2] layer [g/m.sup.2] layer [g/m.sup.2] 1 232 PVOH 4.6 PE 35 2 232 Starch 6.7 PE 35 3 190 Starch 8 PP 20 4 190 PVOH 5 PP 20 5 232 PVOH 4.5 PE 35 6 225 Starch 2.8 PE 15 7 225 Starch 2.8 PP 20 8 232 PVOH 6.3 PE 15 9 232 PVOH 6.3 PP 20 REF 232 — — PE 35

(14) The properties of the packaging material of the invention are summarized in table 2. WVTR and COBB1800 were only determined for some of the test points.

(15) As can be seen in table 2, the packaging materials of the invention showed excellent barrier properties.

(16) All the samples were thereafter converted into packages whereupon the barrier properties were measured. The OTR, WVTR and COBB1800 of the converted packages did not differ significantly from those of the packaging material samples.

(17) TABLE-US-00002 TABLE 2 OTR WVTR COBB1800 Test point [cc/m.sup.2 * day * atm] [g/m.sup.2] [g/m.sup.2] 1 3 1.8 2 8 2.3 3 13.8 2.1 0.5 4 2.8 1.7 0.2 5 0.8 2 6 16 7 13 8 3.4 3.8 9 1.6 2.3 REF 840 2