EP1054808B1

EP1054808B1 - A method for the manufacture of a filling and emptying opening for a liquid packing container

Info

Publication number: EP1054808B1
Application number: EP98949018A
Authority: EP
Inventors: Hannu Kyykoski
Original assignee: UPM Kymmene Oy
Current assignee: UPM Kymmene Oy
Priority date: 1997-10-22
Filing date: 1998-10-19
Publication date: 2004-04-14
Anticipated expiration: 2018-10-19
Also published as: FI974024A0; FI974024A; DE69823234T2; EP1054808A1; FI104811B; WO1999020531A1; DE69823234D1

Description

Background to the invention

The invention relates to a method of making a fill and/or drain opening to a packaging container intended for liquid material, which packaging container either partially or entirely is made of a packaging laminate comprising layers of fibre-based material and thermoplastic, and which opening is later equipped with a detachable pull tab, in which method
a hole of predetermined size and shape is formed on a basic laminate comprising at least one support layer of fibre-based material and at least one first thermoplastic layer,
the hole in the basic laminate and the edges of the hole are covered on the side of the basic laminate comprising at least one first thermoplastic layer with at least one second thermoplastic layer,
the surface of the basic laminate opposite to the at least one first thermoplastic layer is laminated with at least one third thermoplastic layer,
at least the second and the third thermoplastic layers attached to opposite sides of the hole in the basic laminate are joined together at the area of the hole with the help of heat and pressure, and
a fill and/or drain opening is formed centrally with respect to the hole in the basic laminate so that the opening is smaller than the hole in the basic laminate whereupon at least a part of the thermoplastic layers joined together at the area of the hole in the basic laminate is left to cover the untreated edge of said hole.

EP-A-0 686 567 discloses the features in the preamble of claim 1.

Disposable liquid packaging containers are nowadays used more and more in the packaging of liquid food stuffs, such as milk, juice and wine. Usually these packaging containers are made of a prefabricated laminated packaging material comprising a support layer of liquid packaging board which is covered on at least one side and typically on both sides with thin liquid- and gas-tight thermoplastic layers, for example polyethylene layers.

Liquid packaging containers are usually also equipped with an opening device of some type, for example a tear-off or cutoff indication or a detachable pull tab which is attached liquid- and gas-tightly on top of the drain opening. Typical examples of liquid packaging containers equipped with opening devices of this type are disclosed, for example, in the US-A-5 653 383 and SE publication 441 666.

An opening device which comprises a drain opening preperforated through the material and a detachable pull tab attached on top of the opening liquid- and gas-tightly, has several advantages since it is easy to use, it can be attached to the packaging material beforehand and it is inexpensive in costs. However, in the packaging of liquid filling materials, special attention should be paid to an efficient isolation of the untreated edge of the packaging laminate exposed in the perforation from the filling agent, since otherwise the filling agent is absorbed to the fibrous support layer impairing the tightness, strength and appearance of the laminate. To prevent absorption it is therefore common that, in addition to the detachable pull tab, a drain opening is also equipped with an internal thermoplastic layer which is placed on the side of the packaging laminate in contact with the filling agent and which covers both the drain opening and the area surrounding the opening. The cover layer is then attached to the pull tab through the drain opening so that the cover layer is torn when the pull tab is removed enabling the discharge of the filling agent through the drain opening. However, then the previously closed untreated edge of the laminate becomes exposed again and filling agent is absorbed to the fibrous support layer during the discharge procedure. This is not desirable for hygienic and esthetic reasons.

In the packaging of sterile filling agents such as sterile milk and sterile juice, aseptic containers are used the structures of which are mainly similar to what is described above. The packaging laminate nevertheless comprises one or several additional layers to improve gas-tightness. Aluminium foil and thermoplastic, for example polyethylene, are usually used as a gas barrier. Then it becomes particularly important to avoid contact between the filling agent and metal, not only during storage in a closed container but also during the discharge phase and when storing the remaining filling agent in the opened container. This concerns especially acidic filling agents, such as juice and wine, because a contact between these filling agents and metal causes a chemical change which affects the taste of the product.

Prior art solutions to avoid the aforesaid problems in aseptic packaging containers equipped with detachable pull tabs have been quite complicated and comprised an internal cover layer the function of which has been to prevent contact of filling agent with the untreated edge of the pour spout and to ensure that an adequate gas barrier is formed between the filling agent and said untreated edge. A substantial limitation of the prior art solutions has also been that the drain opening equipped with an internal cover layer can not be used as the fill opening of the packaging container since the cover layer has to be attached to the laminate already during its manufacturing stage thus closing the opening. This type of a structure is presented, for example in the SE publication 441 666 already mentioned above.

From the above-mentioned US-A-5 653 383 on the other hand, opening arrangements are known which at least in principle would be suitable for use as fill openings as well, since in them the pull tab is located only on the external surface of the packaging container. The solutions described nevertheless involve certain problems related both to the opening arrangement itself and the general structure of the packaging material. When both the closing of the untreated edge and the closing flap itself are realised with the help of separate flaps fitted only at the area of the hole in the basic laminate, the opening when closed is formed so much thicker than the rest of the packaging laminate that the rolls used in the storage of packaging material are no longer usable. On the other hand, the closing of the untreated edge with a separate flap means that the packaging laminate through which a hole for the manufacture of the drain opening is perforated must already as such meet the requirements set in relation to gas- and liquid-tightness at least as far as the outer surface of the container is concerned, since the flap in question does not contribute to the meeting of these requirements. Such a flap used in the closing of the untreated edge also has to be separately aligned in relation to the hole in the packaging laminate and attached to the edges of the hole, which makes the manufacture also in this part a complex process demanding precision.

Brief description of the invention

The purpose of this invention is to provide a method for making a fill and/or drain opening that involves none of the problems mentioned above. A method according to the invention is characterized in that said at least one second thermoplastic layer, which is used to close the untreated edge of the hole in the basic laminate on the side of the basic laminate which already has at least one thermoplastic layer, is laminated over the entire basic laminate. With this method several substantial advantages are achieved. One of the most central of these advantages is that the thermoplastic layer already in the basic laminate and the thermoplastic layer laminated on top of it and used in the closing of the untreated edge can be optimized in relation to properties. Thus the thermoplastic layer already in the basic laminate can be selected as such that it has optimal adherence to the basic layer of fibre-based material even at the expense of other properties such as gas- and liquid-tightness. These properties can then be taken care of with the help of a thermoplastic layer used in the closing of the untreated edge. It is known that foils with the best barrier properties adhere best to thermoplastic layers and not so much to layers of fibre-based material such as board. On the other hand, the foil used in the closing of the untreated edge can now be selected better also in relation to the properties important in view of closing the untreated edge of the fibre layer as gas- and liquid-tightly as possible. Furthermore the layer used in the closing of the untreated edge can be laminated in an entirely conventional manner since it is now intended to cover the entire basic laminate and no special solutions are required to align it in relation to the hole in the basic laminate.

The third thermoplastic layer to be laminated on the surface of the basic laminate opposite to the first thermoplastic layer forming a part of the basic laminate is extruded as a barrier multi layer foil comprising ethylene alpha olefin. Preferably at least one layer of the barrier multi layer foil settling against the support layer of fibre-based material comprises over 50%, such as 80% ethylene alpha olefin. This way an optimal adherence to the support layer of fibre-based material is achieved and also good barrier properties so that the thermoplastic creating the barrier properties is not the outermost layer.

To improve barrier properties or to create them, if other thermoplastic layers do not have this property, the first thermoplastic layer forming a part of the basic laminate can comprise ethylene alpha olefin.

To achieve barrier properties it is also possible to proceed so that at least one second thermoplastic layer to be laminated on top of the first thermoplastic layer forming a part of the basic laminate is extruded as a barrier multi layer foil.

Since gas- and liquid-tightness thus is now achieved at least for the outer surface of the packaging laminate with the help of at least two thermoplastic layers, the properties of the thermoplastic layer participating in the closing of the untreated edge can be optimised also in relation to a procedure where a fill and/or drain opening is formed by bringing the thermoplastic layers covering the hole in the basic laminate to purse up to the edges of the hole and by treating them so that they are shaped and will close gas- and liquid-tightly the untreated edge of the hole in the basic laminate between them. This way all the plastic around the area of the hole is brought to participate in the closing of the untreated edge which makes the closing extremely reliable. The pursing up can be encouraged by blowing hot air to the centre of the hole in the basic laminate.

It is also possible to proceed more conventionally to form the opening so that the opening is formed by punching and that the remaining parts of at least the second and third thermoplastic layers joined together and bordering the formed opening are heated to a plasticizing temperature and treated so that they are shaped and will close gas- and liquid-tightly the untreated edge of the hole in the basic laminate between them.

According to the invention, the closing of the opening is carried out with a detachable pull tab attached from the outside and therefore the opening can preferably be used both as a fill opening and as a drain opening.

Brief description of the figures

In the following, the invention is described more closely with reference to the attached drawing the figure of which shows a cross-section of one example embodiment of a fill and/or drain opening according to the invention.

Detailed description of a preferred embodiment

In the figure, a packaging laminate 1 is shown, through the layer 3 of fibre-based material and the first thermoplastic layer 4 laminated on top of it forming the basic laminate 2 of said packaging laminate a hole is opened, the untreated edge of the basic laminate bordering the hole being marked with a reference number 5. After this, the basic laminate 2 is covered on opposite sides with a second and a third

thermoplastic layer

6 and 7, the latter of which is thus located on top of the first thermoplastic layer 4. After this the

layers

6 and 7 are joined together at the area of the hole with the help of heat and pressure. After this the forming of the actual fill and/or drain opening follows. The opening is formed preferably between the broken lines 8 in the figure by bringing the

thermoplastic layers

6 and 7 covering the hole in the basic laminate 2 to purse up to the edges of the hole and by treating them so that they are shaped and will close gas- and liquid-tightly the untreated edge 5 of the hole in the basic laminate between them. This way it is possible to avoid air bubbles being entrapped in between the

thermoplastic layers

6 and 7. The pursing up can be effected by different types of known heating methods. It can also be effected or it can be otherwise encouraged by blowing hot air to the centre of the hole in the basic laminate. Naturally the opening between the broken lines 8 can be opened also by punching but in that case not all of the plastic at the area of the hole can be used in the closing of the untreated edge, as in the method described earlier.

The third thermoplastic layer 6 to be laminated on the surface of the basic laminate opposite to the first thermoplastic layer 4 forming a part of the basic laminate 2 is extruded as a barrier multi layer foil comprising ethylene alpha olefin, such as the Dow Chemical Company's AFFINITY ® PT 1450 polyolefin plastomer. This multi layer foil can comprise, for example, five layers extruded simultaneously with the same extruder. Then for example two of the layers settling against the support layer 3 of fibre-based material can comprise over 50%, such as 80%, of said polyolefin plastomer, the rest being LDPE. The rest of the layers of the barrier multi layer foil in question can be for example LDPE. This way an optimal adherence to the support layer of fibre-based material is achieved and also good barrier properties so that the thermoplastic creating the barrier properties is not the outermost layer to be in contact with the product to be packaged.

To improve the barrier properties or to create them. if other thermoplastic layers do not have this property, the first thermoplastic layer 4 forming a part of the basic laminate can comprise a suitable barrier plastic, such as ethylene alpha olefin mentioned above.

To achieve barrier properties it is also possible to proceed so that the at least one second thermoplastic layer 7 to be laminated on top of the first thermoplastic layer 4 forming a part of the basic laminate is extruded as a barrier multi layer foil in the same way as described above with respect to layer 6.

Above the invention is described only on the basis of one example embodiment and it is understandable that the structure described can to some extent be modified without deviating from the scope of protection defined by the attached claims. Thus the basic laminate used can contain before perforation also more than one thermoplastic layers or also for example a barrier layer of aluminium. The number and nature of the layers included in the basic laminate is defined primarily on the basis of the intended use of the packaging container. Similarly the nature and number of the layers to be laminated on top of the basic laminate and thus participating in the closing of the untreated edge of the hole is defined primarily on the basis of the desired properties of the packaging container in each case. The layer composition of a ready-made packaging laminate is naturally optimized so that it meets the desired requirements with respect to both the packaging laminate itself and the closing of the untreated edge of the hole made in the basic laminate. In a method according to the invention, the layers essential for the closing of the untreated edge are utilized optimally also in other parts of the packaging laminate whereupon extra thermoplastic layers unnecessary with respect to each intended use can be avoided.

Claims

A method for making a fill and/or drain opening on a packaging container intended for liquid materials, which either partially or entirely is made of a packaging laminate comprising layers of fibre-based material and thermoplastic, and which opening is later equipped with a detachable pull tab, in which method a hole of predetermined size and shape is formed in a basic laminate (2) of the packaging laminate (1), comprising at least one support layer (3) of fibre-based material and at least one first thermoplastic layer (4),
the hole and its edges (5) in the basic laminate are covered on the side of the basic laminate comprising at least one first thermoplastic layer (4) with at least one second thermoplastic layer (7),
the surface of the basic laminate opposite to at least one first thermoplastic layer (4) is laminated with at least one third thermoplastic layer (6),
at least the second and the third thermoplastic layers (6, 7) attached to opposite sides of the hole in the basic laminate are joined together at the area of the hole with the help of heat and pressure, and
a fill and/or drain opening is formed centrally with respect to the hole in the basic laminate so that the opening is smaller than the hole in the basic laminate whereupon at least a part of the thermoplastic layers (6, 7) joined together at the area of the hole in the basic laminate are left to cover the untreated edge (5) of said hole, wherein said at least one second thermoplastic layer (7) is laminated over the entire basic laminate (2), and
characterized in that said at least one third thermoplastic layer (6) is extruded as a barrier multi layer foil comprising ethylene alpha olefin.
A method according to claim 1, characterized in that at least one layer of the barrier multi layer foil settling against the support layer (3) of fibre-based material comprises over 50 %, such as 80 %, ethylene alpha olefin.
A method according to claim 1 or 2, characterized in that said at least one first thermoplastic layer (4) comprises ethylene alpha olefin.
A method according to one of the claims 1-3, characterized in that said at least one second thermoplastic layer (7) is extruded as a barrier multi layer foil.
A method according to one of the claims 1-4,
characterized in that the opening is formed by bringing the thermoplastic layers (6, 7) covering the hole in the basic laminate (2) to purse up to the edges of the hole and by treating them so that they are shaped and will close gas- and liquid-tightly the untreated edge (5) of the hole in the basic laminate (2) between them.
A method according to claim 5, characterized in that the pursing up is encouraged by blowing hot air to the centre of the hole in the basic laminate.
A method according to one of the claims 1-4, characterized in that the opening is formed by punching and that the remaining parts of the at least second and third thermoplastic layers (6, 7) joined together and bordering the opening formed are heated to a plasticizing temperature and they are treated so that they are shaped and will close gas- and liquid-tightly the untreated edge of the hole in the basic laminate between them.