Stackable package

Abstract

A package (1) formed from a tube (2) made of a paper material (3), the package having a first closed end (4), a second closed end (5), and a longitudinal seal (6) extending between the first closed end (4) and the second closed end (5), the paper material (3) having a first surface (7) arranged to form an outer surface of the package (1), a longitudinal direction (L) of the paper material (3) extending in parallel with the longitudinal seal (6), wherein a static friction coefficient (µs) between two portions of the first surface (7) is 0.10-0.20 when measured according to SS-ISO 15359:2011 using first and second test pieces (T1, T2) cut from the paper material (3), the first test piece (T1) being arranged on the table and the second test piece (T2) being arranged on the sled, the longitudinal direction (L) of the paper material (3) in the first test piece (T1) being oriented in perpendicular to the pulling direction (P) of the sled, and the longitudinal direction (L) of the paper material (3) in the second test piece (T2) being oriented in parallel to the pulling direction (P) of the sled.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of packaging.BACKGROUND

[0002] Plastics is still the predominant packaging material in the world. However, due to the enormous problems of plastic waste and the concern about carbon dioxide emissions, there is a great demand for alternative packaging solutions.

[0003] Paper is a very attractive alternative to plastics since it is easily recyclable, biodegradable and formed from a renewable material. However, the properties of paper are very different from those of plastics, which means that replacing plastics with paper typically requires new package designs and / or significant investments in new machinery. The unwillingness to adopt new designs and make the necessary investments has hampered the transformation to eco-friendly packaging.

[0004] Packages may be stacked during storage. The packages may for example be stacked on a warehouse floor on a pallet, such as a EU-pallet. The aim of the present disclosure is to provide an improved stackable package.SUMMARY

[0005] The present inventors have found that several benefits may be achieved by substituting the plastic used to form package with a paper, said paper package being formed from a paper tube.

[0006] In particular, it has been realized that by providing a paper package which achieves a lower friction between the outer surface of the paper package and the outer surface of a neighbouring paper package when the packages are stacked in a crosswise configuration, handling of the packages may be facilitated.

[0007] That the packages are stacked in a crosswise manner typically means that the machine direction of the paper of a first packages is as least partly aligned with the cross-direction of a paper of a second package.

[0008] An objective of the present invention is to provide a package with reduced environmental impact. A further objective is to provide a package which may improve handling of the packages.

[0009] In particular, the package of the present disclosure may provide benefits during the handling of packages stacked on top of each other, such as during storage or transportation.

[0010] According to a first aspect of the present disclosure, a package formed from a tube made of a paper material is provided, the package having a first closed end, a second closed end, and a longitudinal seal extending between the first closed end and the second closed end, the paper material having a first surface arranged to form an outer surface of the package, a longitudinal direction of the paper material extending in parallel with the longitudinal seal, wherein a static friction coefficient between two portions of the first surface is 0.10-0.20 when measured according to SS-ISO 15359:2011 using first and second test pieces cut from the paper material, the first test piece being arranged on the table and the second test piece being arranged on the sled, the longitudinal direction of the paper material in the first test piece being oriented in perpendicular to the pulling direction of the sled, and the longitudinal direction of the paper material in the second test piece being oriented in parallel to the pulling direction of the sled.

[0011] Thus, during the testing, the surfaces of the test pieces are oriented such that the friction is measured between the longitudinal direction of the paper material, and a direction being perpendicular to the direction of the paper material, along the surface of the paper.

[0012] By arranging the test pieces such that the longitudinal direction of the paper in the first test piece is perpendicular to the longitudinal direction of the second test piece when determining the static friction coefficient, the determined friction coefficient simulates the friction between two packages as they are typically stacked onto each other.

[0013] Preferably, the longitudinal direction is the machine direction of the paper. In that case, the static frictional coefficient between the cross-direction (CD) and the machine direction (MD) of the outer surface of the paper material is 0.10-0.20.

[0014] The static friction coefficient is calculated from the force required to initiate movement of the first test piece in relation to the second test piece. In friction tests conducted of a variety of plastic packaging materials together with the paper material of the present disclosure, the static friction coefficient of the paper material was found to be lower than the static friction coefficient of the plastic packaging material. Thereby, stacking and de-stacking of the packages by e.g. a warehouse worker may be facilitated since the force required to initiate movement of one package, in relation neighbouring packages, is reduced.

[0015] According to an embodiment, a kinetic friction coefficient between two portions of the first surface is 0.08-0.16 when measured according to SS-ISO 15359:2011 using two test pieces cut from the paper material.

[0016] The kinetic friction coefficient is calculated from the force required to continue the movement of the first test piece in relation to the second test piece after movement has been initiated and the test pieces has begun moving at constant speed relative each other.

[0017] Similar to the static friction coefficient, the kinetic friction coefficient of the paper material of the present disclosure was shown to be lower than for plastic packaging materials, thus facilitating handling of the packages, such as stacking and de-stacking.

[0018] The first surface is of the paper material is preferably uncoated.

[0019] The package of the present invention may be used for a variety of uses, the dimensions and properties of the package material being adapted to the application at hand. Thus, as long as the paper material is suitable for use in a stackable package and has a friction coefficient of 0.10-0.20 according to SS-ISO 15359:2011 between the longitudinal direction of the paper material of a first test piece cut from the package, and the direction perpendicular to the longitudinal direction of a second test piece cut from the package, it falls within the subject matter of claim 1.

[0020] The package may be either gusseted or non-gusseted. Benefits of a gusseted tube are that thicker packages can be obtained while the width of the tube can be reduced. If the width of the packaging machine is limited, gussets may thus enable a greater circumference. Gussets also have a stabilizing effect. However, for some or packaging machines, a non-gusseted package may be preferred.

[0021] In one example, the paper material is a kraft paper. The kraft paper may for example be a white kraft paper comprising at least 80% virgin fibres. In one embodiment, essentially all fibres of the kraft paper are virgin fibres. The virgin fibres are preferably predominantly softwood fibres.

[0022] The kraft paper may also unbleached. Preferably, essentially all fibres of such a kraft paper are unbleached virgin fibres. The unbleached virgin fibres are preferably predominantly softwood fibres.

[0023] The paper material may in one example have a strain-at-break in the machine direction (the machine direction typically corresponding to the longitudinal direction of the package and paper material) of 2.5%-6.0%, such as 3.2%-5.5%, when measured according to ISO 1924-3:2005. This has been shown to provide optimal balance between runnability in the packaging machine and strength and durability of the final package.

[0024] The strain-at-break of the paper material is preferably higher in the cross direction (CD, which is typically perpendicular to the longitudinal direction of the package) than in the machine direction. For example, it may be at least 7.0% when measured according to ISO 1924-3:2005 in the CD. An upper limit may be 9.5 %.

[0025] The tensile energy absorption (TEA) of the paper material measured according to ISO 1924-3:2005 is preferably at least 150 J / m2, such as at least 250 J / m2 in the machine direction (MD) and at least 200 J / m2, such as at least 350 J / m2 in the cross direction (CD).

[0026] According to an embodiment, the paper material has a grammage (excluding any coating) of 40-130 g / m2, such as 70-120 g / m2 when measured according to ISO 536:2019.

[0027] According to an embodiment, the package has a cuboid shape.

[0028] By providing a package having a cuboid shape, stacking and transportation of the package may be facilitated. The term cuboid shape does in the present disclosure relate to a shape having six rectangular faces, the corners being 90-degree angles. The faces of the cuboid may have rounded corners as long.

[0029] According to an embodiment, an inside of the package is coated with a sealing layer, such as a heat-sealable layer. This sealing layer is provided on a second surface of the paper material.

[0030] The provision of an internal sealing layer, such as a heat-seal layer, may facilitate sealing in the packaging machine. However, there are alternative sealing techniques that do not require a sealing layer, such as gluing, ultrasonic sealing and pressure sealing.

[0031] The sealing layer may also provide water vapour barrier properties.

[0032] According to an embodiment, the sealing layer has a coat weight of 5-30 g / m2. For example, the sealing layer may have a grammage of 5-20 g / m2.

[0033] According to an embodiment, at least one of the first and second closed ends is closed by a seal.

[0034] The term seal / sealed should in the present disclosure be understood as referring to a closure which do not permit opening without breaking or damaging of the package or seal. For example, it may refer to a closure including a heat-sealable material or an adhesive.

[0035] Thus, by providing one or both ends closed ends of the package with a seal, a durable closing of the package may be achieved, which further allows for stacking of the filled packages without risking that the packages are accidentally opened.

[0036] According to an embodiment, at least one of the first and second closed ends is closed by a fin seal.

[0037] One benefit of providing a lap seal as the longitudinal seal is that it is significantly stronger than e.g. a fin seal. Furthermore, a lap seal results in a thinner structure than a folded fin seal, which may for example be beneficial when the tube is stored on a roll before being used to form the package.

[0038] According to an embodiment, at least one of the first and second closed ends is closed by a cross bottom closure.

[0039] One benefit of providing at least one end of the closed ends with a cross bottom closure is that a more block-shaped package may be provided. A more block-shaped package may both facilitate stacking and provide for more space efficient transportation of the packages.

[0040] According to an embodiment, the longitudinal seal is a lap seal.

[0041] One benefit of providing a lap seal as the longitudinal seal is that it is significantly stronger than e.g. a fin seal. Furthermore, a lap seal results in a thinner structure than a folded fin seal, which may for example be beneficial when the tube is stored on a roll before being used to form the package.

[0042] The overlap of the lap seal may be in the range of 10-50 mm.

[0043] Alternatively, the longitudinal seal may be any other type of seal, such as a fin seal. A fin seal may for example be beneficial in embodiments where durability is less crucial, and where the appearance of the fin seal is preferred.

[0044] In an embodiment, a length of the package, as measured from the first closed end to the second closed end, is two times the width of the package when filled.

[0045] This ratio allows for stacking of the packages in configurations which may be particularly beneficial with respect to stability of the stack and handling of the packages.BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Fig 1 is a perspective view of a package according to an embodiment of the present disclosure, Fig 2 is a perspective view of a part of a paper material for forming a package according to an embodiment of the present disclosure, Fig 3 schematically illustrates a test set up for determining the friction of a paper material according to SS-ISO 15359:2011 Fig. 4a is a schematic front view of a stack of packages according to an embodiment of the present disclosure, Fig. 4b is a schematic side view of the stack of packages, Fig. 4c is a schematic top view of a stack of packages, Fig. 5a is a schematic front view of an alternative stack of packages according to an embodiment of the present disclosure, Fig. 5b is a schematic side view of the alternative stack of packages, Fig. 5c is a schematic top view of the alternative stack of packages. DETAILED DESCRIPTION

[0047] Fig. 1 shows a package 1. The package 1 is formed from a tube 2 made of a paper material 3, the tube 2 being formed from a paper sheet bent into a tubular shape and attached to itself along its longitudinal edges. A longitudinal seal 6 is formed where the longitudinal edges of the paper sheet 2 are connected. The package 1 further comprises a first closed end 4 and a second closed end 5, and the longitudinal seal 6 extends from the first closed end 4 to the second closed end 5. The closed ends 4, 5 is in this example sealed ends.

[0048] The paper material 3 has a longitudinal direction L extending in parallel with the longitudinal seal 6. The longitudinal direction of the paper material 3 typically correspond to a machine direction MD of the paper material, and a direction transverse to the longitudinal direction of the paper material 6 typically correspond to a cross-direction CD of the paper material 3.

[0049] The longitudinal seal 6 may be a lap seal. The lap seal may be obtained by heat-sealing. In such case, the paper is coated with a heat-sealable layer at an inner surface (further discussed in relation to fig. 2). Alternatively, the longitudinal seal may be achieved in other ways, such as by gluing.

[0050] The closed ends 4, 5 may be achieved in several different ways, such as by sealing through the application of a glue or by heat-sealing. The ends may for example be sealed by a fin seal or a cross bottom seal.

[0051] The size and proportions of the packages could be varied depending on the intended use. For example, in some cases, the package could have a length of 750-850 mm, a circumference of 1100-1500 mm, and a width of 350-450 mm when filled. These proportions may provide for a package which is suitable for being stacked on a EU-pallet. However, other dimensions may as well be used.

[0052] Fig. 2, shows part of a sheet of the paper material 3 before being formed into the package. That is, before forming of the longitudinal seal 6 and of the first and second closed ends 4, 5. The paper material 3 has a first surface 7 arranged to form an outer surface of the package 1, and a second surface 8 opposite to the first surface.

[0053] The first surface 7 is configured to form an outer surface of the package 1. The first surface 7 is thus the surface of the package material which may contact objects surrounding the package 1. For example, the outer surface may contact an outer surface of a further package when the packages are stacked on top of each other in a warehouse, or during transportation.

[0054] The second surface 8 may be configured to come into contact with the filling of the package 1. Alternatively, the inner surface 8 may be coated with a sealing layer, such as a heat-sealable layer.

[0055] If not coated with a sealing layer, the grammage of the paper material 3 is typically in the range of 40-130 g / m 2< , such as 70-120 g / m 2< . When coated with a sealing layer, the total grammage of the paper material 3 and the coating is typically in the sage of 45-160 g / m2, preferably 75-150 g / m 2< . In the present disclosure, grammage is measured according to ISO 536:2019.

[0056] The paper material preferably has a strain-at-break in the machine direction of 2.5.0%-6.0%, such as 3.2-5.5 %. More preferably, the strain-at-break value in the MD is in the range of 3.5%-5.0%. In the present example, the machine direction corresponds to the longitudinal direction of the paper material 6. The strain-at-break was measured according to ISO 1924-3:2005.

[0057] In Fig. 2, the forming of a non-gusseted tube 2 is illustrated. However, the tube 2 for forming the package 1 may be either gusseted or non-gusseted. Benefits of a gusseted tube are that thicker packages can be obtained while the width of the tube can be reduced. If the width of the packaging machine is limited, gussets may thus enable a greater circumference. Gussets also have a stabilizing effect.

[0058] A static friction coefficient µ s between two portions of the first surface 7, is 0.10-0.20 when measured according to SS-ISO 15359:2011 using two test pieces T1, T2 cut from the paper material 3, and being oriented such that they extend in perpendicular horizontal directions during the testing. In a preferred embodiment, the static friction coefficient µ s is 0.14-0.18.

[0059] Furthermore, a kinetic friction coefficient µ k between two portions of the first surface 7, is 0.08-0.16 when measured according to SS-ISO 15359:2011 using the same set up as for determining the static friction coefficient. For example, the kinetic friction coefficient µ k may be 0.12-0.16.

[0060] The manner of determining the friction coefficients is further described in relation to Fig. 3.

[0061] Fig. 3 schematically illustrates a set up for determining the friction coefficient between two portions of the first surface 7 according to SS-ISO 15359:2011. The test method includes attaching first and second test pieces to a table and a sled respectively and pulling the sled along the table while recording the force required to overcome the friction between the test pieces.

[0062] Thus, to determine the static friction coefficient µ s between two portions of the first surface 7 of the paper material 3, a first test piece T1 and a second test piece T2 was first cut out from the paper material 3, the first test piece T1 being at least 60 x 130 mm to provide for a sliding surface, and the second test piece T2 being at least 60 x 60 mm. The first test piece T1 was attached to a table with the first side 7 facing outwards, and the second test piece T2 was attached to a sled with the first side 7 facing outwards.

[0063] The second test piece T2 was oriented in such a way on the sled that the longitudinal direction L of the surface 7 of the paper material 3 in the second test piece T2 extended in parallel with the pull direction P of the sled.

[0064] The first test piece T1 attached to the table, was oriented such that the longitudinal direction L of the surface 7 of the paper material 3 in the first test piece T1 extended perpendicular to the pull direction P of the sled.

[0065] In a preferred embodiment, the test pieces T1, T2 were oriented such that the machine direction (MD) of the first test piece T1 was arranged perpendicular to the pulling direction P of the sled, while the machine direction (MD) of the second test piece T2 was arranged in parallel with to the pulling direction P of the sled.

[0066] The sled with the second test piece T2 attached was then lowered slowly towards the table with the first test piece T1 attached, allowing the first surfaces 7 of the test pieces T1, T2 to meet simultaneously over their entire contact area.

[0067] Thereafter, movement of the sled was initiated, allowing the test pieces T1, T2 to slide in relation to each other. The initial force required to initiate the sliding was recorded. By dividing the recorded initial force by the weight of the sleigh multiplied with as the gravity g, the static friction coefficient was obtained.

[0068] The test was conducted three times using different test pieces from the same material to obtain a mean value of the static friction coefficient.

[0069] The kinetic friction coefficient µ k was determined during the same test rounds as the static friction coefficient. To determine the kinetic friction coefficient µ s , the force required for moving the sled at constant speed was recorded. The kinetic friction coefficient was then calculated using the same equation as for the static friction coefficient.

[0070] Figs. 4a-4c illustrates one possible stacking configuration for packages of the present disclosure. The packages are in this case stacked on top of a Euro-pallet. The stacks shown in figs. 4a-4c shows three rows of packages stacked upon each other, each row consisting of three packages. In reality, the stack may have a lower of higher number of rows. Furthermore, each row may comprise a higher or lower number of packages.

[0071] Fig. 4a, which is a front view of the stack of packages, shows that the packages are stacked in a crosswise manner with respect to each row. Thus, in the in the top and bottom rows, the short ends of the packages are visible, while the long end of a package is visible in the middle row. Further combining this view with what is shown in Fig. 4b, which is a side view of the same stack, and Fig. 4c, which is a top view of the same stack, it is even more clear that the orientation of the packages varies within each row such that the pattern of one row is mirrored in the adjacent rows.

[0072] In this preferred stacking configuration, the longitudinal direction of the paper material of a first package 1 is thus typically perpendicular to the longitudinal direction of the paper material of at least part of the neighbouring package(s) in the stacks, both within and between the rows. By stacking the packages in a crosswise manner, a very stable and compact stack may be provided.

[0073] The handling of packages stacked in the way illustrated in Figs. 4a-4c may be facilitated by the packages having a friction coefficient as specified in claim 1 of the present disclosure as compared to plastic packaging materials. This is due to the fact that the lower friction coefficient facilitates sliding of a package 1 from and / or onto the stack.

[0074] By providing the packages with specific proportions, such as a length of the package being two times the width of the package when filled, stacking in the illustrated configuration may be optimized, as the practically the entire surface of the pallet is utilized, while a stable and balanced configuration is achieved.

[0075] Many other stacking configurations in which the packages are arranged in a somewhat crosswise manner are also conceivable. For example, in one possible alternative configuration, all packages of a first row could be arranged in the same direction, while all packages of a neighbouring row could be oriented in a direction perpendicular to the packages of the first row. This alternative stacking configuration is illustrated in Figs. 5a-5c.

[0076] To prevent unintentional sliding of the packages in relation to each other during e.g. transportation, the entire stack may be wrapped in any suitable wrapping material or stabilized in any other suitable way.

[0077] Furthermore, the properties of the paper material could be altered to optimize the static friction coefficient, aiming at providing a friction which is high enough to prevent unintentional sliding, but low enough to still facilitate stacking and restacking.EXAMPLE

[0078] In an example, the package 1 was produced from a pure white kraft pulp paper consisting entirely of virgin softwood fibres. Typical properties the paper is shown in table 1 below. The table shows the properties of the paper before being provided with any coating, such as a sealing layer. As already mentioned, many different paper materials could be used for the package of the present disclosure, this is thus only one example. Table 1. Typical properties the paper material.Property Unit Value Method Grammageg / m 2< 120ISO 536Thicknessµm150ISO 534Tensile strengthkN / mMD12.0ISO 1924-3kN / mCD6.6Tensile indexNm / gMD100ISO 1924-3Nm / gCD55Strain-at-break%MD4.3ISO 1924-3%CD9.0TEAJ / m 2< MD300ISO 1924-3J / m 2< CD400TEA IndexJ / gMD2.5ISO 1924-3J / gCD3.3Tear strengthmNMD1650ISO 1974mNCD2050Tear indexmNm 2< / gMD13.5ISO 1974mNm 2< / gCD17.0Burst strengthkPaMD660ISO 2758Burst indexkPam 2< / gCD5.5Roughnessml / minWS1000ISO 8791-2TS1900Brightness%85ISO 2470Cobb 6osg / m 2< WS30ISO 535Moisture%7.5ISO 287

[0079] The friction coefficients of the paper material according to SS-ISO 15359:2011 was determined through the procedure described in relation to Fig. 3. The friction coefficients were determined during three test rounds performed on different test pieces of the paper material. Average static and kinetic friction coefficients were then calculated based on the forces recorded during the three test rounds, as shown in Table 2. Table 2. Determined static and kinetic friction coefficients of the paper material.Friction first surface (MD) to first surface (CD) Static frictionTest round 10.179Test round 10.156Test round 10.148Mean value, static friction0.16Kinetic frictionTest round 10.137Test round 10.142Test round 10.13Mean value, kinetic friction0.14

[0080] In addition to the paper, corresponding friction tests were conducted on four different plastic materials (Plastic 1- Plastic 4). It can be seen in Table 3 that both the static and the kinetic friction coefficients for the paper material were lower than for the plastic materials. Table 3. Friction coefficients of the paper material compared to different plastic materials.Paper material of the present disclosurePlastic 1Plastic 2Plastic 3Plastic 4Static friction0.160.390.220.370.35Kinetic friction0.140.360.200.360.36

Claims

1. A package (1) formed from a tube (2) made of a paper material (3), the package having a first closed end (4), a second closed end (5), and a longitudinal seal (6) extending between the first closed end (4) and the second closed end (5), the paper material (3) having a first surface (7) arranged to form an outer surface of the package (1), a longitudinal direction (L) of the paper material (3) extending in parallel with the longitudinal seal (6), wherein a static friction coefficient (µs) between two portions of the first surface (7) is 0.10-0.20 when measured according to SS-ISO 15359:2011 using first and second test pieces (T1, T2) cut from the paper material (3), the first test piece (T1) being arranged on the table and the second test piece (T2) being arranged on the sled, the longitudinal direction (L) of the paper material (3) in the first test piece (T1) being oriented in perpendicular to the pulling direction (P) of the sled, and the longitudinal direction (L) of the paper material (3) in the second test piece (T2) being oriented in parallel to the pulling direction (P) of the sled.

2. The package (1) of claim 1, wherein a kinetic friction coefficient (µk) between the two portions of the first surface (7) is 0.08-0.16 when measured according to SS-ISO 15359:2011 using the two test pieces (T1, T2) , arranged as defined in claim 1.

3. The package (1) of any one of the preceding claims, wherein the package (1) has a cuboid shape.

4. The package (1) of any one of the preceding claims, wherein the paper material (3) has a grammage of 40-130 g / m2, such as 70-120 g / m2, when measured according to ISO 1924-3:2005 and excluding any coating.

5. The package (1) of any one of the preceding claims, wherein an inside of the package (1) is coated with a sealing layer, such as a heat-sealable layer.

6. The package (1) of any one of the preceding claims, wherein at least one of the first and second closed ends (4, 5) is closed by a seal.

7. The package (1) of any one of the preceding claims, wherein at least one of the first and second closed ends (4, 5) is closed by a fin seal.

8. The package (1) of any one of the preceding claims, wherein at least one of the first and second closed ends (4, 5) is closed by a cross bottom closure.

9. The package (1) of any one of the preceding claims, wherein the longitudinal seal is a lap seal.

10. The package (1) of any one of the preceding claims, wherein the static friction coefficient (µs) is 0.14-0.18.

11. The package (1) of any one of claims 2-10, wherein the kinetic friction coefficient is 0.12-0.16.

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