Method for manufacturing a cup having a flat rim for attaching a cover, blank for forming a side wall of a cup and cup

Abstract

The invention concerns a method for manufacturing a cup (1) having a flat rim (4) for attaching a cover, comprising the following method steps: providing a single-side barrier material coated paper blank (100) for forming a side wall (2) of the cup (1), wherein the blank (100) has a first surface (101) adapted to form the inside of the side wall (2) and a second surface (102) adapted to form the outside of the side wall (2), wherein the first surface (101) is covered with the barrier material coating, applying a heat seal lacquer (103) in a top portion (112) of the second surface of the blank (100), the top portion (112) being intended to form the flat rim (4) of the cup (1); forming the side wall (2) of the cup (1) by joining two edges of the blank (100) along a side seam, providing a bottom (3) and joining the bottom (3) with the side wall (2) such that the top portion (112) is arranged at a top edge (22) of the side wall (2) facing away from the bottom (3); curling the top edge (22) of the side wall (2) thereby forming a curled rim, wherein the heat seal lacquer (103) is arranged on an inner surface of the curled rim; flattening the curled rim thereby forming a flat rim (4).

Description

[0001] Method for manufacturing a cup having a flat rim for attaching a cover, blank for forming a side wall of a cup and cup.

[0002] The invention concerns a method for manufacturing a cup having a flat rim for attaching a cover. The invention further concerns a blank for forming a side wall of a cup having a flat rim for attaching a cover. Additionally, the invention concerns a paper cup.

[0003] Cups with a flat rim for attaching a cover are typically used in food packaging, e.g., for packaging yogurt or other dairy products. In general, a cover in the form of a foil is attached to the flat rim to seal the cup. Before use, the cover may be peeled of or otherwise removed by a user to access the dairy product in the cup.

[0004] For a long time there exist dairy product cups with a flat rim which are completely made from plastics. As part of an effort to make dairy packaging more sustainable, those plastic cups are currently exchanged by paper-based cups. Paper-based cups with a flat rim typically are made from double-sided polyethylene coated paper board, which provides good moisture barrier properties as well as good heat-sealing properties on both sides. Whereas a moisture barrier is at least required on the inside of the cup, good heat-sealing properties are desired in both surfaces of the sidewall of the such cups. This is because forming of the flat rim of such cups typically involves curling a top edge of the side wall and flattening the curled edge by pressing the curled edge. During this process, several layers of the side wall join to form the flat rim. This process takes advantage of the heat-sealing properties provided on both surfaces of the side wall. If the heat-sealing properties of one or both surfaces of the side wall are poor or not available at all, it is, however, hardly possible to manufacture a cup with a stable flat rim.

[0005] It would be advantageous to use single-side polyethylene coated paper board for forming the side wall of such cups with a flat rim. Thereby, the quantity of plastics in the resulting cup could be reduced. Using single-side polyethylene coated paper board, however, comes with the disadvantage that only one surface of the paper board has heat-sealing properties. As a result, the layers of the side wall do not properly connect during the flattening process. Against this background the invention aims at providing a process for reliably forming paper cups with a flat rim with reduced amount of polyethylene.

[0006] According to an aspect of the i n v e n t i o n , there is provided a method for manufacturing a cup having a flat rim for attaching a cover, comprising the following method steps: providing a single-side barrier material coated paper blank for forming a side wall of the cup, wherein the blank has a first surface adapted to form the inside of the side wall and a second surface adapted to form the outside of the side wall, wherein the first surface is covered with the barrier material coating, applying a heat seal lacquer in a top portion of the second surface of the blank, the top portion being intended to form the flat rim of the cup; forming the side wall of the cup by joining two edges of the blank along a side seam, providing a bottom and joining the bottom with the side wall such that the top portion is arranged at a top edge of the side wall facing away from the bottom; curling the top edge of the side wall thereby forming a curled rim, wherein the heat seal lacquer is arranged on an inner surface of the curled rim; flattening the curled rim thereby forming a flat rim.

[0007] The inventive method allows for manufacturing of a cup with a flat rim from a single-side barrier material coated paper blank. The term “barrier material” refers to a material that provides moisture barrier properties, and preferably also heat sealing properties. By using a single-side barrier material coated paper blank, the amount of barrier material in the resulting cup is reduced as compared to prior art cups made from double-side polyethylene coated paper. By applying the heat seal lacquer in the top portion of the second surface of the blank heat-sealing properties are provided to the second surface of the blank which is free from the barrier material coating present on the first surface. Thus, heat sealing properties can be obtained on the second surface of the blank even though this second surface generally comes without such heat-sealing properties. The heat-sealing properties in the top portion on the second surface improve joining the layers of the side wall during flattening the curled rim and thereby facilitate forming a stable flat rim of the cup.

[0008] The barrier material is preferably polyethylene (PE). Alternatively, the barrier material may be polyethylene terephthalate (PET), polysiloxane, clay coating or a varnish.

[0009] In the following, advantageous embodiments of the invention will be disclosed. Applying a heat seal lacquer

[0010] According to a preferred embodiment of the invention, the heat seal lacquer is a water-based heat seal lacquer. The heat seal lacquer may comprise a polyolefin-based dispersion.

[0011] According to a preferred embodiment of the invention, applying the heat seal lacquer comprises applying the heat seal lacquer only in the top portion. This means that the remaining portion of the second surface is free from heat seal lacquer. This embodiment comes with the advantage that heat-sealing properties are only provided to the second surface in a portion where those properties are required to reliably form the flat rim, namely the top portion. The remaining portions of the second surface do not require heat-sealing properties. Superfluous application of lacquer can be avoided and the material costs and production costs can be reduced.

[0012] According to a preferred embodiment of the invention, the top portion has a height in the range of 0,5 mm to 15 mm, preferably in the range of 7 mm to 11 mm, more preferably in the range of 8 mm to 10 mm. A top portion having a height in the indicated range may be used to form in internal layer in a flat rim having a configuration with three layers of the side wall. The layers are preferably brought into a folded configuration by the curling and flattening steps of the inventive method. The flat rim can have a radial dimension, a so-called flange length, in the range of 0.5 mm to 5 mm, preferably in the range of 1 mm to 4 mm, for example a flange length of 3.5 mm.

[0013] According to a preferred embodiment of the invention, applying the heat seal lacquer includes applying the heat seal lacquer using a roller, preferably an anilox roller. Applying the heat seal lacquer using a roller, in particular an anilox roller, has the advantage that the quantity of heat seal lacquer can be precisely dosed. The roller, in particular anilox roller, may have a total transfer volume in the range of 20 cm3to 30 cm3. Preferably, the heat seal lacquer is applied during a printing process including printing artwork and / or applying the water vapor varnish and / or applying the anti-curling agent. The printing process may involve using several rollers for printing the heat seal lacquer separately from the artwork and / or water vapor varnish and / or anti-curling agent.

[0014] Preferably, applying the heat seal lacquer results in a heat seal lacquer layer in the top portion of the second surface having a weight per quare in the range between 1 gsm and 5 gsm, preferably in the range between 2 gsm and 3 gsm, more preferably in the range between 2 gsm and 2.5 gsm. According to a preferred embodiment of the invention, an anti-moisture barrier varnish is applied to the second surface, preferably to a remaining portion of the second surface below the top portion. The anti-moisture barrier varnish, also known as water vapor varnish, may be applied to the second surface, in particular, to the second surface outside the top portion. Thereby, the moisture protection of the outside of the cup may be improved. Protecting the second surface from the influence of moisture may avoid unwanted soaking of the side wall and help to maintain the stability of the cup even under the influence of moisture on the outside of the cup. Optionally, an anti-curling agent may be applied to the second surface, in particular, to the second surface outside the top portion. Thereby, the resistance of the cup against unwanted curling may be improved. The stability of the cup may be further improved.

[0015] Forming the side wall of the cup

[0016] According to a preferred embodiment of the invention, forming the side wall of the cup by joining two edges of the blank along a side seam comprises joining by heat-sealing. Here, the heat-sealing properties are provided by the barrier material on the first surface, which is the outside of the cup.

[0017] Joining the bottom and the side wall

[0018] According to a preferred embodiment of the invention, joining the bottom with the side wall comprises joining by heat-sealing. Here, the heat-sealing properties are provided by the barrier material on the first surface, which is the outside of the cup.

[0019] Curling the top edge of the side wall

[0020] According to a preferred embodiment of the invention, - before curling the top edge of the side wall - the top edge of the side wall is moisturized. That means that the side wall of the cup is in an uncurled condition when being moisturized. Moisturizing may facilitate or even promote curling of the top edge. Moisturizing can be carried out using a sponge. The sponge may be brought into contact with the top edge of the side wall, preferably only with top edge of the side wall and not the remaining portion of the side wall below the top edge.

[0021] According to a preferred embodiment of the invention, curling the top edge includes a first curling step and a second curling step, wherein heat is applied to the top edge of the side wall between the first and second curling step. The first curling step may create a slightly curled condition of the top edge of the side wall whereas the second curling step creates a more strongly curled condition. As a result of the first curling step the top edge may by bend over without touching the remaining portion of the side wall, in particular without touching the remaining portion of the second surface of the side wall - the exterior surface of the cup. As a result of the second curling step, the curled top edge preferably touches the remaining portion of the side wall, in particular the remaining portion of the second surface of the side wall - the exterior surface of the cup. Thus, in the second curling more paper may be put inside the curl provided by the first curling step and / or the curl provided in the first curling step may be compressed further. The first and second curling steps are preferably carried out using respective curling tools, here a first and a second curling tool. By applying heat to the top edge of the side wall the heat seal lacquer as well as the barrier material on the first surface may be activated so that the layers of the side wall may be joined to form the flat rim in the flattening step following the curling step. Heating is preferably provided by ultrasonic heating equipment. Heating may be carried out in a single step or in two or more consecutive steps.

[0022] According to a preferred embodiment of the invention, applying heat to the top edge of the side wall comprises heating the top edge using a heater having a temperature in the range from 350°C to 400°C. Heating using a heater having a temperature in the mentioned range promotes proper activation of the heat seal lacquer on the second surface of the side wall and the barrier material coating on the first surface of the side wall.

[0023] According to a preferred embodiment of the invention, applying heat to the top edge of the side wall includes applying heat to a part of the inside of the side wall that is facing away from an interior of the cup as result of the first curling step. In other word, the heat may be applied from outside the cup. This facilitates arrangement of the heating equipment.

[0024] Flattening the curled rim

[0025] According to a preferred embodiment of the invention, flattening the curled rim includes applying pressure to the curled rim. Preferably, pressure is applied using an upper member and a lower member, wherein the curled rim is arranged between the upper and lower member. The upper and lower member are preferably moved towards each other thereby pressing the curled rim from above and from below. The flatness can be controlled by the amount of pressure that is exerted onto the curled edge.

[0026] According to a preferred embodiment of the invention, flattening the curled rim includes joining two or more layers of the top edge of the side wall that form the curled rim by means of the heat seal lacquer. The two or more layers may be joined using the heat seal lacquer. For example, two sections of the second surface where heat seal lacquer is arranged can touch each other so that the heat seal lacquer is arranged between both the two sections. By curling and flattening the top edge of the side wall, a flat rim can be obtained that includes several layers of the sidewall. Different interfaces may exist between those layers. Where a part of the second surface of the sidewall touches another part of the second surface, heat seal lacquer interfaces the touching surfaces and facilitates joining those surfaces. Where a part of the first surface of the side wall touches a part of the second surface of the side wall heat seal lacquer and barrier material coating interact to join the surfaces.

[0027] Blank

[0028] According to a further aspect of the i n v e n t i o n , there is provided a single side barrier material coated paper blank for forming a side wall of a cup, wherein the blank has a first surface adapted to form the inside of the side wall and a second surface adapted to form the outside of the side wall, wherein the first surface is covered with a barrier material coating, wherein a heat seal lacquer is arranged in a top portion of the second surface of the blank, the top portion being intended to form the flat rim of the cup.

[0029] The inventive blank allows to manufacturing of a cup with a flat rim with reduced amount of barrier material.

[0030] Paper cup

[0031] According to a further aspect of the i n v e n t i o n , there is provided a paper cup comprising a bottom and a side wall attached to the bottom, wherein an inside of the side wall is covered with a barrier material coating, wherein a flat rim for attaching a cover is arranged at a top edge of the side wall facing away from the bottom, wherein the flat rim has been formed by curling the top edge of the side wall thereby forming a curled rim, wherein a heat seal lacquer is arranged on an inner surface of the curled rim and flattening the curled rim thereby forming the flat rim.

[0032] The inventive paper cup can be reliably formed with reduced amount of barrier material.

[0033] The preferred embodiments and optional features elucidated with respect to the method for manufacturing a cup having a flat rim may - alone or in combination - be employed with the inventive blank and / or the inventive paper cup. Further details and advantages of the invention will be elucidated in the following with reference to the embodiments shown in the figures.

[0034] Fig. 1 depicts a first surface of a blank according to an exemplary embodiment of the present invention;

[0035] Fig. 2 depicts a second surface of a blank according to an exemplary embodiment of the present invention;

[0036] Fig. 3 depicts different conditions of a top rim of a side wall of a cup during manufacturing according to an embodiment of the inventive method in sectional views;

[0037] Fig. 4 depicts a detailed sectional view of the top rim of the cup after curling according to an embodiment of the inventive method;

[0038] Fig. 5 depicts a detailed sectional view of the top rim of the cup after flattening according to an embodiment of the inventive method;

[0039] Fig. 6 depicts a paper cup according to an embodiment of the invention.

[0040] Fig. 1 and Fig. 2 depict two opposing surfaces of a paper blank 100 for forming a side wall 2 of a paper cup 1 having a flat rim 4 for attaching a cover. Those paper cups are suited for holding dairy products like yogurt. The blank 100 has an outline represented by a solid line. Different hatchings show different areas of the blank that will be discussed in the following.

[0041] The paper blank is cut from single-side barrier material coated paper which means that only one side of the paper blank 100 has a barrier material coating while the other side is free from coating with the barrier material present on the first surface. The barrier material is polyethylene. Fig. 1 depicts a first surface 101 of the paper blank 100 which is the one coated with polyethylene. The polyethylene may be low density polyethylene (LDPE) with a grammage in the range of 20 gsm to 30 gsm, preferably in the range of 23 gsm to 26 gsm, for example 24 gsm. As visible in Fig. 1 , the complete first surface 101 of the blank 100 is covered with polyethylene. This surface is intended to form the inside of the side wall 2 of the paper cup 1 that is to be manufactured. Fig. 2 depicts the second surface 102 of the blank 100, which is the surface intended to form the outside of the side wall 2 of the resulting paper cup 1 . In a top portion 112 of the second surface 102 a heat seal lacquer 103 is arranged. The top portion 112 is intended to form the flat rim 4 of the cup. Thus, the top section of blank 100 is provided with heat-sealing properties on both the first surface 101 and the second surface 102 which is important for forming a stable flat rim during the manufacturing process. The remaining part of the second surface is provided with an anti-moisture barrier varnish 104, optionally comprising an anti-curling agent.

[0042] As part of the inventive method for manufacturing a cup 1 having a flat rim 4 for attaching a cover, a single-side polyethylene coated paper blank 100 is provided. The method comprises applying the heat seal lacquer 103 in the top portion 112 of the second surface of the blank 100. Fig. 1 and 2 depict an example of a blank 100 that is treated this way. The heat seal lacquer 103 may be water-based and may be applied using a roller, preferably an anilox roller.

[0043] The inventive method further includes forming the side wall 2 of the cup 1 , see Fig. 6, by joining two edges of the blank 100 along a side seam 5. Then a bottom 3 is provided and joined with the side wall 2 such that the top portion 112 is arranged at a top edge 22 of the side wall 2 facing away from the bottom 3. As a result of those operations, a cup 1 is provided having a side wall 2 that has an unfolded top rim. In other words, curling and flattening of the rim in order to obtain the flat rim 4 of the inventive paper cup is still to be done.

[0044] The top edge 22 of the side wall 2 is preferable moisturized before curling so as to weaken the material of the top edge 22 and facilitate curling. Moisturizing may be done using a sponge.

[0045] With reference to Fig. 3, the steps of curling and flattening will be elucidated. Curling the top edge 22 of the side wall 2 - thereby forming a curled rim - is carried out in a two step process. In a first curling step, the top edge 22 is bent over without touching the remaining portion of the side wall 2. The result of the first curling step is depicted in Fig. 3a. It is visible that the top edge 22, which is bend over, does not touch the remaining portion of the second surface of the side wall 2, in other words the exterior surface of the cup 1 .

[0046] After the first curling step, when the side wall 2 has the configuration shown inf Fig.3a, heat is applied to the side wall 2, in particular to the top edge 22 of the side wall 2 as indicated by the arrows H. The heat activates both, the polyethylene coating on the first surface 101 and the heat sealing lacquer 103 in the top portion 112 of the second surface 102. Due to the activation of the polyethylene and the heat seal lacquer, the layers of the side wall 2 may be joined in the following flattening step. Heating may be provided in two steps. After heating and before the flattening step, a second curling step is carried out, the result of which is depicted in Fig. 3b. In the second curling step, more paper is put inside the curl provided by the first curling step and the curl is compressed. Fig. 3b shows that the curled top edge touches the remaining portion of the side wall 2, in particular the remaining portion of the second surface 102 of the side wall - the exterior surface of the cup.

[0047] The two-step curling process provides a curled rim which is flattened in a following flattening step. Flattening is achieved by applying pressure to the curled rim, e.g. by compressing the curled rim from above and below. Fig. 3c shows the flat rim 4 obtained in the flattening step.

[0048] Fig. 4 depicts a detail of the curled top edge after both the curling steps. The radial dimension of the curled top edge is indicated by reference sign X. The top edge of the side wall is curled such that is almost touches, preferably touches the exterior surface of the side wall, here the second surface 102.

[0049] Fig. 5 depicts a detail of the flat rim 4 after the curling and flattening steps. The radial dimension of the flat rim 4 is increased by AX as compared with the curled top edge before the flattening step, wherein AX is preferably in the range of 2 mm to 3 mm, more preferably in the range of 1.5 mm to 2.5 mm. The flat rim can have a radial dimension, a so-called flange length, in the range of 0.5 mm to 5 mm, preferably in the range of 1 mm to 4 mm, for example a flange length of 3.5 mm.

[0050] As depicted in Fig. 5, the layers of the side wall 2 are in a folded configuration by the curling and flattening steps. At the interface between the upper layer and the middle layer (referred to as interface A), polyethylene coating is facing the heat seal lacquer. At the interface between the middle layer and the lower layer (referred to as interface B), heat seal lacquer is facing heat seal lacquer. Thus, the heat seal lacquer facilitates joining the layers of the side wall 2 in both interfaces.

[0051] Fig. 6 shows a paper cup 1 that can be obtained by the inventive manufacturing method. The paper cup 1 comprises a bottom 3 and a side wall 2 attached to the bottom 3. The inside of the side wall 2 is covered with a polyethylene coating and a flat rim 4 for attaching a cover is arranged at a top edge 22 of the side wall 2 facing away from the bottom 3. The flat rim 4 has been formed by curling the top edge 22 of the side wall 2 thereby forming a curled rim, wherein a heat seal lacquer 103 is arranged on an inner surface of the curled rim and flattening the curled rim thereby forming the flat rim. Reference signs

[0052] 1 paper cup

[0053] 2 side wall

[0054] 3 bottom

[0055] 4 flat rim

[0056] 22 top edge

[0057] 100 paper blank

[0058] 101 first surface

[0059] 102 second surface

[0060] 103 heat seal lacquer

[0061] 104 anti-moisture barrier varnish

[0062] 112 top portion

[0063] 121 top edge

[0064] 122 bottom edge

[0065] 123 side edge

[0066] 124 side edge

[0067] 125 top corner

[0068] 126 top corner

[0069] A, B interface

[0070] H heat

Claims

Patent Claims:

1. Method for manufacturing a cup (1) having a flat rim (4) for attaching a cover, comprising the following method steps: providing a single-side barrier material coated paper blank (100) for forming a side wall (2) of the cup (1), wherein the blank (100) has a first surface (101) adapted to form the inside of the side wall (2) and a second surface (102) adapted to form the outside of the side wall (2), wherein the first surface (101) is covered with the barrier material coating, wherein the barrier material is a material that provides moisture barrier properties, and preferably also heat sealing properties, applying a heat seal lacquer (103) in a top portion (112) of the second surface of the blank (100), the top portion (112) being intended to form the flat rim (4) of the cup (1); forming the side wall (2) of the cup (1) by joining two edges of the blank (100) along a side seam, providing a bottom (3) and joining the bottom (3) with the side wall (2) such that the top portion (112) is arranged at a top edge (22) of the side wall (2) facing away from the bottom (3); curling the top edge (22) of the side wall (2) thereby forming a curled rim, wherein the heat seal lacquer (103) is arranged on an inner surface of the curled rim; flattening the curled rim thereby forming a flat rim (4).

2. Method according to claim 1 , wherein the barrier material is polyethylene or polyethylene terephthalate or polysiloxane or clay coating or a varnish.

3. Method according to any of the preceding claims, wherein the heat seal lacquer (103) is a water-based heat seal lacquer.

4. Method according to any of the preceding claims, wherein applying the heat seal lacquer (103) comprises applying the heat seal lacquer (103) only in the top portion (112).

5. Method according to claim 4, wherein the top portion (112) has a height in the range of 0,5 mm to 15 mm, preferably in the range of 7 mm to 11 mm, more preferably in the range of 8 mm to 10 mm.

6. Method according to any of the preceding claims, wherein applying the heat seal lacquer (103) includes applying the heat seal lacquer using a roller, preferably an anilox roller.

7. Method according to any of the preceding claims, wherein an anti-moisture barrier varnish (104) is applied to the second surface, preferably to a remaining portion of the second surface below the top portion (112).

8. Method according to any of the preceding claims, wherein - before curling the top edge (22) of the side wall (2) - the top edge (22) of the side wall (2) is moisturized.

9. Method according to any of the preceding claims, wherein curling the top edge (22) includes a first curling step and a second curling step, wherein heat is applied to the top edge (22) of the side wall (2) between the first and second curling step.

10. Method according to claim 9, wherein applying heat to the top edge (22) of the side wall (2) comprises heating the top edge (22) using a heater having a temperature in the range from 350°C to 400°C.11 . Method according to any of claims 9 or 10, wherein applying heat to the top edge (22) of the side wall (2) includes applying heat to a part of the inside of the side wall (2) that is facing away from an interior of the cup (1) as result of the first curling step.

12. Method according to any of the preceding claims, wherein flattening the curled rim includes applying pressure to the curled rim.

13. Method according to any of the preceding claims, wherein flattening the curled rim includes joining two or more layers of the top edge (22) of the side wall (2) that form the curled rim by means of the heat seal lacquer (103).

14. Single-side barrier material coated paper blank (100) for forming a side wall (2) of a cup (1) having a flat rim (4) for attaching a cover, wherein the blank (100) has a first surface (101) adapted to form the inside of the side wall (2) and a second surface (102) adapted to form the outside of the side wall (2), wherein the first surface (101) is covered with a barrier material coating, wherein the barrier material is a material that provides moisture barrier properties, and preferably also heat sealing properties, characterized in thata heat seal lacquer (103) is arranged in a top portion (112) of the second surface of the blank (100), the top portion (112) being intended to form the flat rim (4) of the cup.

15. Paper cup (1) comprising a bottom (3) and a side wall (2) attached to the bottom (3), wherein an inside of the side wall (2) is covered with a barrier material coating, wherein the barrier material is a material that provides moisture barrier properties, and preferably also heat sealing properties, wherein a flat rim (4) for attaching a cover is arranged at a top edge (22) of the side wall (2) facing away from the bottom (3), characterized in that the flat rim has been formed by curling the top edge (22) of the side wall (2) thereby forming a curled rim, wherein a heat seal lacquer (103) is arranged on an inner surface of the curled rim and flattening the curled rim thereby forming the flat rim.

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