COATED PAPERBOARD FOR BEVERAGE CONTAINER CARRIERS AND CORRESPONDING BEVERAGE CONTAINER CARRIER

Abstract

The invention relates to a coated paperboard (10) for beverage container carriers (30) comprising: a paperboard substrate (12), a dispersion coating layer (18, 20) on each side (14, 16) of the paperboard substrate (12), wherein the paperboard substrate (12) comprises wet strength agents in an amount in a range from 0 wt % to 0.05 wt %, based on the dry solid content of the substrate (12) and sizing agents for making the paperboard (12) substrate more hydrophobic, wherein the sizing agents are present in an amount of 0.15 wt %, especially in a range from 0.15 wt % to 0.5 wt %, based on the dry solid content of the substrate (12). The invention further relates to a beverage container carrier (30) comprising or being made from the aforementioned coated paperboard (10).

Claims

1. A coated paperboard for beverage container carriers comprising: a paperboard substrate, a dispersion coating layer on each side of the paperboard substrate, wherein the paperboard substrate comprises wet strength agents in an amount in a range from 0 wt % to 0.05 wt %, based on a dry solid content of the paperboard substrate and sizing agents for making the paperboard substrate more hydrophobic, wherein the sizing agents are present in an amount of 0.15 wt %, based on the dry solid content of the paperboard substrate.

2. The paperboard according to claim 1, wherein the sizing agents are selected from a group consisting of: acidic sizing agents, basic sizing agents, neutral sizing agents or a mixture of at least two of these types.

3. The paperboard according to claim 1, wherein the sizing agents are selected from a group consisting of: alkyl ketene dimer, alkyl succinic anhydride, rosin or a mixture thereof.

4. The paperboard according to claim 1, wherein at least one of the dispersion coating layers is a dispersion coating layer applied in one single layer or two sub-layers.

5. The paperboard according to claim 1, wherein at least one of the dispersion coating layers comprises latex, polyolefin, or both.

6. The paperboard according to claim 5, wherein the latex is selected from the group consisting of: styrene-butadiene latex, styrene-acrylate latex, acrylate latex, vinyl acetate latex, vinyl acetate-acrylate latex, styrene-butadiene-acrylonitrile latex, styrene-acrylate-acrylonitrile latex, styrene-maleic anhydride latex, styrene-acrylate-maleic anhydride latex, or a mixture of any combination of these latexes.

7. The paperboard according to claim 5, wherein the at least one dispersion coating layer further comprises pigments.

8. The paperboard according to claim 5, wherein the at least one dispersion coating layer further comprises additives in an amount in a range 0.1 wt % and 5 wt %, wherein the additives include at least one of thickening agents, defoaming or antifoaming agents, dispersing aids, additional pigments, cross-linkers, slip additives, fillers, release agents, preservatives and antiblocking agents.

9. The paperboard according to claim 5, wherein the at least one dispersion coating layer further comprises a cross-linker, which is an agent reacting with carboxyl, hydroxyl groups, or both.

10. The paperboard according to claim 9, wherein the cross-linker is selected from a group consisting of: Ammonium Zirconium Carbonate, Potassium Zirconium Carbonate, Potassium Zirconium Acetate, melamine formaldehyde resin, urea formaldehyde resin, Glyoxal, Imidazoline derivatives, di-aldehyde polysaccharides and any combinations of these group members.

11. The paperboard according to claim 1, wherein the wet strength agents comprise at least one selected from the group consisting of: urea resins, melamine resins, polyamidoamine-epichlorhydrine resins, PAM-glyoxal resins, glyoxal, glyoxal resins, and dialdehyde-starch.

12. The paperboard according to claim 1, wherein the COBB 3600 called water absorption rate of the coated paperboard after 3600 s is 20 gsm.

13. The paperboard according to claim 1, wherein the water absorption of the coated paperboard after being wetted in 60 minutes is 20 wt.

14. The paperboard according to claim 1, wherein the Wick index of the coated paperboard is 3 kg/m.sup.2.

15. A beverage container carrier comprising the coated paperboard according to claim 1.

16. The beverage container carrier according to claim 15, wherein the carrier comprises a handle formed by a structure in the coated paperboard, a structure made of the coated paperboard, or both.

17. The beverage container carrier according to claim 15, wherein the main component of this carrier is a blank of the coated paperboard.

18. The beverage container carrier according to claim 15, wherein a shape of the carrier is that of open ended tubular carton with a top wall, two side walls and a bottom wall which is formed by wrapping the coated paperboard about the beverage containers.

Description

[0046] Further features of the present invention will become apparent from the example and figures, wherein:

[0047] FIG. 1 shows a schematic sectional view of a coated paperboard according to a preferred embodiment of the invention,

[0048] FIG. 2 shows a beverage container carrier according to a preferred embodiment of the invention on a test stand for testing the handle integrity (HI) and

[0049] In FIG. 1 a sheet of coated paperboard 10 is shown in a schematic sectional view. The coated paperboard 10 comprises a paperboard substrate 12 having a first side 14 (upper side in the figure) and a second side 16 (bottom side in the figure), wherein each of these sides 14, 16 is coated by a respective a dispersion coating layer 18, 20.

[0050] The paperboard substrate 12, which is a base of the board 10, comprises (i) wet strength agents in an amount of less than 0.5 kg/ton and at least 1.5 kg/ton internal sizing agents. The dispersion coating layers 18, 20 are aq. dispersion barrier coatings applied on both sides 14, 16 of the paperboard substrate 12. In the example shown here in FIG. 1 the dispersion coating layer 18 on the first side 14 is a dispersion coating layer 22 applied in two sub-layers and the dispersion coating layer 20 on the second side 14 is a dispersion coating layer 24 applied in one single layer.

[0051] Within the paperboard substrate 12 a wet strength addition is replaced at least in part by a higher sizing dosage (HS BB: Hard Sized Baseboard) in combination with barrier sealing of the outer plies by means of a dispersion coating (DB: Dispersion Barrier) on each side (dispersion coating layers 18, 20) of the paperboard substrate 12 (HS BB). The dispersion coating layers 18, 20 prevent wetting from the surfaces 26, 28 of the board 10 and the higher sizing dosage within the paperboard substrate 12 will prevent raw edge penetration, while the board 10 is recyclable. These measures reduce strength loss when wetted compared to the material of conventional beverage container carriers made from paperboard and improves recyclability at the same time.

[0052] The material as shown in FIG. 1 is particularly suitable for the manufacture of beverage container carriers 30 as shown in FIG. 2. The coating layer 22 applied in two layers is preferably on the outside of the respective beverage container carrier 30 and the coating layer 24 applied in one layer is preferably on the inside.

[0053] FIG. 2 shows a package 32 with a plurality of beverage containers 34 and a beverage container carrier 30 on a test stand 36 for testing the handle integrity of a handle 38 of the beverage container carrier 30.

[0054] The beverage containers 34 of the package 32 shown in FIG. 2 are beverage cans. The illustrated package 32 comprises an assembly of six beverage containers 34 enclosed in an open ended tubular carton which is formed by wrapping about the beverage containers 34, while the beverage containers 34 are grouped in double row, transversely aligned triplets, a cut and scored blank 40 of the coated paperboard 10 and securing the ends of the blank 40 in a manner which results in the carton walls being tightly drawn about the group of beverage containers 34 so as to form a tightly wrapped package 32 and insure that the beverage containers 34 will be retained in the carton under normal handling of the package 32.

[0055] The package structure is formed by wrapping the blank 40 about the group of beverage containers 34 which are arranged in double row and in transversely alignment, and securing the ends of the blank 40 while the bottom wall forming panels are drawn inwardly of the sidewall forming panels by the folding operations (not explicitly shown). The beverage containers 34 are of well-known configuration. It will be understood that the blank 40 may be modified to adapt it to the packaging of beverage bottles and other articles of the same or similar configuration, i.e. other kinds of beverage containers 34.

[0056] The blank 40 is an elongate rectangular sheet of the coated paperboard 10, which is of suitable weight or gauge and which is cut and scored so that it is symmetrical about a longitudinal center line running intermediate its side edges. It is divided by longitudinally spaced hinge forming folding lines 42 (score lines) which extend in parallel relation transversely of the blank 40, and divide it into a top wall 44 forming center panel section, adjoining sidewall 46 forming panel sections and bottom wall 48 forming end panel sections, the latter having at their terminal end portions end panel connecting strips or locking and latching strips of relatively narrow width, the inner edges of which are defined by the hinge score lines, respectively (not shown). The center panel section (forming the top wall 44) comprises semi-elliptically opposed lines for forming package carrying holes 50, which serve as the handle 38. In other words, the handle 38 is directly formed by structures of blank 40 or the coated paperboard 10.

[0057] The test stand 36 is arranged for testing the handle integrity of the handle 38. In a corresponding handle integrity test the filled package 32 is clamped or physically held down while a pulling device 52 of the test stand holds the handle 38. For this purpose, the device here in the example uses finger-shaped elements 54. The pulling device 52 pulls the handle 38 of the (multi-pack) carrier 30 until it fails. A load cell measures the force as the handle 38 is pulled to failure. The result of the test includes the peak force (Fmax) at failure and a description of the location of the handle failure.

[0058] The generally accepted rule in beverage packaging is that the force required to cause handle failure must be at least three times the weight of the package 32.

[0059] Wet handle strength testing is performed by submerging a filled package 32 in water for 3 minutes, then testing the handle strength of the handle 38 as in the dry test. Naturally the paperboard 10 and glue used in the package 32 must be designed for a wet environment.

[0060] Table 1 shows a comparison of the properties of the coated paperboard 10 according to a preferred embodiment of the invention compared to boards of different design. The coated paperboard 10 according to the embodiment of the invention is called HS BB+DB (hard sized base board HS BB with dispersion barrier DB). The reference board (REF) is a conventional Kraft Back Board (KBB) according to prior art, which comprises a high amount of wet strength agents. KKB+DB (REF 2) is the reference (comprising a high amount of wet strength agents), but with a dispersion barrier. HS BB (REF 3) is a base board that comprises a high amount of internal sizing agents; HS BB+DB is the concept according to the invention (INV), comprising a high amount of internal sizing agents and a dispersion barrier.

TABLE-US-00001 TABLE 1 comparison of the properties of a coated paper board according to one embodiment of the invention compared to paper boards of a different design. Property Unit DB = Dispersion KBB KBB KBB + DB HS BB HS BB + DB Barrier (REF) (REF) (REF 2) (REF 3) (INV) HS BB = Hard Sized Baseboard Wetting time Time/min 0 (Dry) 60 60 60 60 Sample KBB KBB KBB + DB HS BB HS BB + DB (Dry) (60) (60) (60) (60) Grammage g/m.sup.2 326.4 326.4 346.6 319 339.7 Grammage relative % 100% 100% 106% 98% 104% to KBB-REF Handle Integrity Fmax(N) 232.69 51.4 154.1 36.32 223.3 (HI) HI relative to KBB- Fmax(N) 233 51 145 37 250 REF grammage Cyclic drop test Cycles to 34.8 2.0 19.7 0.8 45.1 (CDT) Failure CDT rel. to KBB Cycles to 35 2 19 1 43 REF grammage Failure Cobb TS g/m2 NA 149 6.3 121 9 Water abs. (Tensile % 6.4 68.4 49.0 51.3 12.1 test sample. Average MD and CD. %) Wick index water 60 kg/m.sup.2 h NA NA 3.28 NA 0.66 min Tensile index GM Nm/g 64.30 9.16 12.57 6.89 32.06 Tensile stiffness kNm/g 5.51 0.53 0.70 0.61 2.76 index GM

[0061] The dispersion coating applied to the HS BB+DB (Inv) was applied to the base board at a coat weight of 6 gsm on the print side and 15 gsm on the back side. The dispersion was a polyolefin dispersion (100%) with no pigments.

[0062] The grammage relative to KKB is the grammage relative to the reference KBB. This is included in the calculation of some of the resultsHI (Handle Integrity) and CDT (cyclic drop test) show both absolute values and values that are weighted to the ref grammage. This because the grammage also influence this value.

[0063] The strength properties for the reference is shown both as dry and after being wetted/immersed in water at 23 C. for 60 minutes. For the other samples (including the HS BB+DB) the strength properties are shown after 60 minutes immersed in water.

[0064] As can be seen from the results, the Handle integrity of carriers made from the reference is highly reduced after the carrier has been immersed in water. The application of a dispersion barrier improves the HI somewhat, while the exchange of wet strength agents to internal sizing agents makes it even worse. By the concept of the invention, the handle integrity also after the carrier has been immersed in water for 60 minutes is almost at the same level as the reference when this is dry.

[0065] Table 2: Board+ISO shows both the methods used and some description of the sample boards. Most of the properties are measured by use of standard methods, while Wick Index (Raw edge water absorption), Cyclic Drop Test (CDT) and Handle Integrity are not standard methods and links to description of these are included.

TABLE-US-00002 TABLE 2 sheet Board + ISO Actual BB = Base Board except pigment coating Board Sizing (AKD, ASA, Rosin or etc or a Basis combination) weight Base Wet (incl. Board Thick- Strength pigment weight ness Sizing Agents # coating) (actual) (actual) kg/ton kg/ton Name g/m.sup.2 g/m.sup.2 m BB BB REF 326 308 502 1.4 0.8 KKB REF 3 319 301 509 2.7 0 HS BB REF 2 6 + 326 + 326 502 1.4 0.8 KKB + 15 = 347 DB HS 6 + 319 + 319 509 2.7 0 BB + 15 = 340 DB

[0066] The wick index defines the edge penetration and is measured by an edge penetration testEWT (Edge Wick Test) according to the following method: paperboard samples are covered on both sides with waterproof tape (or, as in the present case, only with existing barrier coating), and cut to a specific size. The samples are conditioned at 23 C., 50% RH for 10 minutes, after which thickness and weight of the samples are measured. Thereafter, the samples are put into a test solution, particularly water, (bath) for a certain period of time. The wick index for is then calculated by the formula:

[00001]$E=\frac{W2-W1}{tl}$

wherein E is the wick index (kg/m2), W1 is the weight before bath (mg), W2 is the weight after bath (mg), t is the thickness (m) and 1 is the total length of the edges of the samples.

REFERENCE SIGNS

[0067] 10 coated paperboard [0068] 12 paperboard substrate [0069] 14 first side [0070] 16 second side [0071] 18 dispersion coating layer (first side) [0072] 20 dispersion coating layer (second side) [0073] 22 layer applied in two sub-layers [0074] 24 layer applied in one single layer [0075] 26 surface (coated paperboard) [0076] 28 surface (coated paperboard) [0077] 30 beverage container carrier [0078] 32 package [0079] 34 beverage container [0080] 36 test stand [0081] 38 handle [0082] 40 blank [0083] 42 folding line [0084] 44 top wall [0085] 46 side wall [0086] 48 bottom wall [0087] 50 package carrying hole [0088] 52 pulling device [0089] 54 finger-shaped elements